Woah.  All that sounds like either bad memory, bad harddrive, or worse (virus/spyware).  If applications just start having all sorts of problems - there is something more fundamental going on then.

A power supply issue would mean that it is either going bad (happens on occasion) or is not powerful enough for all of the equipment in the computer.  I'm no expert on how to determine this, but usually go by what the motherboard states as a minimum and then add 50-100 Watts for good measure.

You may want to take the computer in for professional servicing - if it's still under warranty, make sure to take advantage of it.

ETA: And svdl's suggestion about overheating/dust is a good thing to pursue (from personal experience that).  If your BIOS has temperature monitoring, you should find out what the safe temperature range is, get into the BIOS on computer startup, and check the running temps.   Some motherboard manufactures provide software that lets you monitor this in Windows and even set alarms.

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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