I want to use an SSD for my OS and apps, and have all other files on WD HD. I know how to move the libraries (Windows 7) to the non boot drive, but how do I set it up so all the temp files, user profiles, etc are on the non-boot drive?

Keep everything except for larger collections of documents on the SSD. Like if you tend to really use the "My Documents" folders for music and stuff, you can simply right-click on "My Documents" and relocate its position. TEMP files can benefit from SSD performance (or a RAM drive if you have a lot of that) so they are generally good to leave there, but the settings for re-mapping the TEMP directories can be found under System > Advanced system settings > Environment Variables. Notice how there are settings for both each user and the system separately.

Software uses the user account folders more and more for storing important files that can impact performance, so unless you have the bad habit of putting huge files right on your desktop(separately relocatable like My Documents), keep the Users folder on the SSD. With todays prices it's not a very good idea to go with a much smaller SSD than 120GB either, even if a 60GB can certainly be workable. (60GB drives usually come with a definite performance hit compared to 120'ish brethren, and larger drives will also last longer write-wise.) With Windows 7 and later, set up a backup schedule to your other drive or an external.

That's helpful. Thanks! I do video editing, so I'm looking at 2 WD drives - one for the library (esp pictures), and the other for the pre-rendered/temp/working files for video projects Does that make sense?

I'm not doing video editing myself beyond sporadic transcoding, but I can't see a fault with that setup so it looks good to me. See if the video editing software has settings of its own when it comes to its temp files as well as checking how big they typically get. For instance I have my Photoshop temp files redirected onto a RAM drive, which is especially nice considering how Photoshop puts up files even when they could easily fit everything into the system RAM. I'd instinctively suspect other Adobe software to behave similarly.

It's actually not such a good idea to put only your OS and apps on an SSD. It's easy to notice the benefit (fast boot time and app startup) but how often do you need to reboot or restart your apps (assuming you have enough RAM, which would be a cheaper upgrade than an SSD)?

The temp files and the user profiles are one of the things you benefit most from having on your SSD.
Libraries are a different matter. It depends what you're talking about exactly.

What shouldn't be on your SSD is movies and to a lesser extent other multimedia files, unless perhaps you're actually working with them.
If you keep around stuff like ISOs or service packs, there's usually no point in keeping them on your SSD either.

In many cases you can easily configure default directories and such. But some other directories are hard-coded like some large system directories containing librairies you don't really need to have on your SSD.
If you want to put some non-configurable directories on a different drive, look into this:
http://en.wikipedia.org/wiki/NTFS_junction_point


Drives for video editing need to be considered carefully.
Having a dedicated hard drive or array for the files you're working on can be useful, sure. But hard drives noisy, bulky and consume power.
Using an SSD for video editing can be even better. Some SSDs are worse than hard drives and others are better.
But maybe you don't need to do anything outside of the ordinary.
The requirements for video editing tasks vary a lot. You need to figure out how much throughput you need if you want to take an intelligent decision, especially if you haven't bought the SSD you're talking about. If you already have it, you could simply try to work with different drives, see what works best and only buy something new the day you're actually faced with an intractable performance problem. Then you could describe that real-world problem and find a solution.

I doesn't usually make sense to have a drive dedicated to pictures.

When I refer to the library, I'm specifically referring to the Windows 7 librairies which contain 4 folders - documents, music, pictures, and videos. My thought is to have those files on a spearate drive - and using the video folder to store the video files that I'm using as source material for projects. The other WD drive would be where I would configure Vegas Pro (the video editing software) to use for the video project files.

What you put in those four "libraries" is entierly up to you. You don't need to put them on another drive in order to put any particular (set of) video files on that drive.

The ideal configuration depends entierly on the exact operations you want to do. Blanket recommendations are worse than useless.
There's a general principle to get good performance with hard drives however: the drive should only work on one thing at a time. So if you read from a file and write to another, it could be useful to read from one drive and write to another. As long as you're not constantly accessing the other stuff on the drives, it doesn't matter what else they contain (pictures, OS, apps and so on). What matters is the files you're actually reading or writing from simultaneously.
SSDs on the other hand can work on several things simultaneously without a huge performance hit.

WD drives are not faster or slower than others. They make several different types of drives with different performance characteristics.

Install the TreeSize utility and run it once in a while to see if any directories on your SSD are growing.

I did this and discovered that the CyberLink PowerDirector video editor was storing zillions of small "temporary" files in the Program Files directory, instead of in tmp, temp, or usr/tmp, and never deleting them. As in 10 GB worth by the time I discovered it. Other applications also display such antisocial behavior (eg, AllRecorder, which does put its (very large) files in a tmp directory, but never deletes them).

Another tool you'll want is EmpTemp, which you can easily set up to delete files from various directories if they haven't been touched for several days.

To remedy the PowerDirector problem, I had to create a junction point to my HDD, then configure EmpTemp to clean it. (Vegas editing software behaves better, but I need PD now and then to recode messed up MPEG files)

One directory you'll be alarmed by is the Windows sxs directory. This can't be moved from C, and grows every time you install an updated system component (eg, driver). My Windows 7 has grown about 10GB after a year or so. By being aggressive, I've kept my C drive around 40GB utilized (out of 80GB total; I was a very early adopter of the X25M). If you get a 120GB SSD you shouldn't have any problems.

Libraries in Win7 are just collections of pointers. What matters is where the underlying folders are located.

In some cases you can use windows options to relocate folders. In other cases you need to change the registry. In still others, you have to use junction points, the windows equivalent of *nix soft links.

Thanks.

I'm thinking I will get a larger SSD and put everything on it except my videos and photos.

I did something similar. The 128GB SSD has OS, apps, the game du jour, and an encrypted folder where docs and profiles for browser, email, and PIM are stored. The HDD has music, video, pictures, and the rest of the game programs.