First, because heat damage can cause such issues, open the case and use compressed air to blow out all the dust from around the processor, heatsink, power supply, and all vents and fans.
Next, clean out all the junk files from your Temp folders and Temporary Internet Files. Then uninstall any programs you don't need, or at least, prevent them from running in the background in "Services" or "msconfig", if they're not necessary. If you've got two antivirus programs installed, remove one. One AV is the best way to go so there's no conflicts between the two. You might even run Chkdsk to attempt to repair any damaged files on the hard drive. (run "chkdsk /f /r /x" from a command prompt, then restart the computer to start the disk check.)
And finally, just in case it's malware, click on the link below and follow ALL of the steps to the letter.
“Expand” the post titled: "Please try this" at the link below:
http://www.cnet.com/forums/post/f742c795-5881-433b-a29b-6d758efe5cd3/
Hope this helps.
Grif
Over the last 2 weeks I've had the following happen seemingly at random, first directly after waking from standby, but now it also happened twice out of nowhere while the PC was running. It's hard to fully investigate the issue while it's happening but there seem to be at least 3 things that are part of this:
1) Internet goes out on my PC, can't even reach the router anymore
2) No programs open anymore, I've tried a lot of different ones, including process explorer, nothing happens. This also causes the PC to not shut down anymore.
3) Some, not all, currently running programs won't close properly and/or crash while closing.
As far as I can tell so far anything that is currently running keeps running however e.g. I can still do stuff in Word etc. if it is open and also still save my work. There is no indication, no errors, it just seemingly randomly "happens", nothing of note in the event viewer, I haven't installed anything recently, everything is up to date and there are no other problems.
Specs (let me know if you need more):
Win 7 Pro x64
Intel i5 4590
16GB RAM

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic