Can anyone give any advice? That is what I am running at the moment, will upgrade soon, but still use the processor in another PC, might as well try to make it as silent as I can...

Your 1 Ghz Pentium-3 CPU have a max heat-dissipation of around 28-30W according to http://users.erols.com/chare/elec.htm

Compare that with my relatively modest XP-1700 that nevertheless dissipates between 57-64W. Nearly twice the heat that must be taken care of. Nevertheless I get away with a Swiftech MCXC370 heatsink + a modest 60mm/3000rpm fan. In your case you can preferably choose the aluminium-variant: MCX370 + an even slower/quieter 60mm 2500rpm fan. 60mm fans below 2500rpm are so quiet that you must open the case and put your ear right next to them, in order to hear them. These Swiftechs 370-sinks are also dead-easy to mount/dismount.

Check them out (but choose another fan): http://www.swiftnets.com/products/mcx370.asp

If you cant fint a 60mm/2000-2500rpm-fan, then buy the next slowest - then you can slow down the speed/noise further with a Zalman FanMate 1 ( http://www.zalman.co.kr/english/product/cnpsfanmate.htm ).

----------------------------------- edit:

Slot?? You mean not an ordinary 370 socket CPU? Hmm.
My advice: Buy a Celeron-II Tualatin 1200Mhz instead, together with the appropriate new motherboard. Other then that; above heatzink-advice still stands.

with Slot cooling there's two heatsinks that would probably fit the bill for u either the VOS32+ (massive heatsink made by globalwin) might block up some RAM slots or the alpha P7125 http://www.below-0.net/belowzero.asp?contenttype=products&menuid=453054338 very nice pin fin heatsink with the copper base........... just make sure that there's some airflow going over them from like a PSU fan or the like...

This is the inside of my case (not my picture though)...

I just received this morning the Fortron 300FPS modified with the Verax fan that Tom's Hardware has been raving about.
I am using my PC strictly for video playback (DVD's AVI's and Tape or satellite broadcast via a Falcon capture card and using Dscaler).
For now, 1Ghz is really enough for that purpose. I am thinking of upgrading to a 2.4Ghz Pentium IV, but first I want to see how silent I can make my current PC (Asus P3BF board and Pentium III 1Ghz processor Slot 1)
At the back of the case, there are two openings for fans (I will purchase two panaflo's for that, running at the minimum speed necessary to keep the case cool.

The Fortron PSU will also (I imagine) be sucking air off the CPU.
To cool one of the heatsink posted by quokked (what about the Alpha...) I was thinking of a less noisy solution than the two fans blowing on the heatsink while screwed on it....
What about using a panaflo running above the cpu&heatsink suspended using a Zalman Fan Bracket.

I was thinking of going for a 90mm one, to get as much air on the heatsink as possible...
Would it work?
Anyone tried this?

By the way, this is a shot of my motherboard: Asus PB3-F



As you can see from the position of the SLOT 1, the heatsink would be facing the front of the case, and the back of the CPU would be paralell to my two fans on the back of the case. This is a waste really as I really wanted the air sucked away from the Heatsink...

But there it goes