Question : Problem: Laptop turning off and slowing down drastically (overheating i think)

I have an Acer Travelmate 2423WXCi, just out of warranty (1 year). Over the past few weeks it started slowing down dramatically at various intervals. Certain processes cpu usage would sky-rocket to a total of 100%, these include system.exe, firefox.exe and svchost.exe among others. I initially thought it was malware so scanned many times with lots of different packages and removed several threats. It started happening again, this time it was also shutting off on its own, mostly when i wasn't using it. I did a complete system restore to rule out malware (re-format, re-partition) problem persists.
Overheating is the only other cause i can come up with. After stripping it down to check the fan and heatsink i have deduced that it is not dust or anything blocking the fan. Does anyone have any suggestions? Are there any heat monitoring tools i can use? Acer's support desk hasn't been any help as yet.
PS: Have checked the HD for errors as well, no problems found.

Answer : Problem: Laptop turning off and slowing down drastically (overheating i think)

did you reapply some heatpaste to the cpu? that can be the cause.