I'll try to channel Mr Fickens for this one:
Is your computer simply 'freezing' all the time or do you get the blue screen crash?
Squarebear's option is a start. You could also try opening up the case and cleaning out all the dust, especially any that's collected on the fans - this could cause overheating which could result in the problems you're having.
On the software side, you could try running the usual virus/spyware checkers and making sure your computer is free of those. Malwarebytes is a good start:
http://www.malwarebytes.org/
There are many others which other users will no doubt recommend.
Also, try updating drivers if available for your existing hardware.