The highest you could go is the 3.00GHz AMD Athlon 6000.

The CPU Chris mentions is an 89w version not the 125w one.  You can also upgrade to a 3.1Ghz 6000+ Brisbane.  I have that processor in two other 531 computers.

Thanks for the info guys.......could you tell me if I would see a noticeable system improvement by switching to the Athlon 64  (seems they are hard to find and rather expensive) or would I be better off upgrading my motherboard? Thanks in advance!

Yes you will see a noticeable difference since you would be going from a single core to a dual core.  The problem as you've already figured out is they are very hard to find.  As for the motherboard, the Dell case has a preprietary front panel connection so you would also have to get a new case and a retail copy of Windows.  Your currently copy is tied to the motherboard and will not install on a non-Dell motherboard.

So if I have the 531s with the single core processor I can upgrade it to any AM2 CPU,even 64 bit x2 ?

The motherboard is ORY206.I do have the latest BIOS.

I apologize for hijacking this thread but it ALMOST answered my question.

Yes you can upgrade to an AMD Athlon 64 X2 Dual Core processor.  Just stay away from the 125w versions as they are to hot for the heatsink/fan in your slim 531.  Problem is they are very hard to find as they are not manufactured anymore.

Yes you can upgrade to an AMD Athlon 64 X2 Dual Core processor.  Just stay away from the 125w versions as they are to hot for the heatsink/fan in your slim 531.  Problem is they are very hard to find as they are not manufactured anymore.

There's a few on Ebay.I should be able to pick one up there.I'm assuming(from reading another thread) that I should try to stay around 65W.That

would put me in the 5000 range??

Hate to revive an old thread, I have the same issue trying to replace an athlon 2650e >> athlon X2 5000+.. In CPUid it shows the core speed at 2.6 GHz which is good, but only shows 1 core. Also in task manager I only have 1 "CPU graph". This is the ORY206 board, like in this thread, and was wondering how I can get my computer to recognize the second core. In device manager it shows two Athlon X2 5000+ 's under Processor tab.