I would also make sure the computer is clean. Does not matter if it's a laptop or desktop, open that baby up and blow it out with clean air. Be sure to concentrate on the heat sink fins and fan blades.

Thanks for the answers guys and to answer yours:
- I mentioned but I'm not using my GPUs (2x ATI 4670HD 1GB DDR3-1600)I, I'm interested in using them tho.
- I'm a PC tech for a living so my Firewall is well configured, my PC is relatively clean and not overheating, my 2 SATA2 HDDs pass SMART tests just fine. I searched for 'Western Digital's Data lifeguard' and found is specifically for EIDE HDDs, thx for the suggestion tho.

I've noticed that only some projects cause the lag. The only way my PC is lagless is by setting the BOINC client in 'Low', 'Below Normal' gives me small lag spikes, so is not optimal. I had Folding@Home GPU and it gave me BSODs and in F@H Forum I read some guy in India at the seems had the same GPU and didn't have problems at all, so my system is not OK, but the lag started with new projects added to the WCG, started a few days ago, before that I never had lag, not even with this PC, and I built about 2 years ago AMD Phenom II X4 3.2Ghz, 2x2GB DDR3-1333, MoBo Asus M4A79XTD Evo, no overclocking. The lag is WCG-related though, I could bet is not my system, even with the small instability problem it has. As an example MPC 64-bit lags when I'm watching DXVA accelerated movies, that use only little CPU.

Anyway, I'm reinstalling Win7 64-bit and I'm going for the Pro version not 'Ultimate' one, maybe is a little lighter.

I have an improved AMD Cooler but I run hot anyway 60+ ºC so I have set the client to 60% CPU usage. The 'while computer is at least lower than x%' is not what I want, because it doesn't help much in the research.

I'll let you know how things workout after the reinstallation tomorrow. Cheers.

Just use 3 cores rather than 4 and you should see no lag whatsoever.

Sorry for my late response, BTW my MoBo died because I tried to take out the cooler and the CPU came off sticked to it without raising uo the CPU socket lever, anyway this Mobo is better (Foxconn A7DA-S v3.0 (2 PCI, 2 PCI-E x1, 2 PCI-E x16, 4 DDR3 DIMM, Audio, Video, Gigabit LAN)). I have overclocked my CPU from 3.4 to 3.6Ghz I could do 3.8 but I need a better Power Supply, the cables overheat at 3.8; maxed my 2 ATI 4670s with the latest Cats 11.10 (with 11.11 preview 3) and is all OK.

@Coleslaw: I searched the site and I found only the PATA one, but anyway my 2 SATA hard drives work fine and both are the typical electromechanical ones. I didn't found

@skgiven: Only 3 cores is not a good solution, is a bad patch for a bad configuration IMO.

@steffen_moeller: My 2 HDDs don't have any heavy activity because of WCG, if the PC is OK WCG doesn't cause that, maybe is their security software, defragmentation utility or something else, maybe a virus, spyware or malicious rootkit.

I use Avast! Home & COMODO Firewall and don't have any extra HDD activity even when I have them active because I deactivate Avast! & COMODO Defense+ for better performance when I'm not introducing/viewing new information.

All projects run just fine in my PC nothing unusual at all, I found strange that you have any problems with any of them.

Sorry but I won't be doing Einstein@Home.

The problem I think it is BOINC related, not WCG related, when all BOINC processes ran on 'Low' priority everything was better, they should ran at least at 'Below Normal' priority to avoid this, I don't know why IBM had to make this change but it was for the worse for me.