Possibility #2: Disorganized Files
Windows operating systems handle file organization in a way that isn’t very intuitive. Basically, they break files up and fit them into gaps in the computer’s memory. As time goes by, these disorganized files can prompt frequent crashes. Luckily, a great optimization solution is built right into Windows-based PCs: the disk defragmentation utility. Although its location on a computer varies, you can generally locate it within the System and Security section inside the Control Panel. By running a defrag once every few months, you may be able to keep those pesky computer crashes at bay.
Possibility #3: Malicious Software
Malicious software can take many different forms. Sometimes, it’s a virus that is accidentally unleashed after opening a strange email; other times, its adware that tags along with other information that is automatically downloaded from a website. Whatever type it is, there’s no question that malicious software can wreak havoc on a computer’s performance. Happily, there are many topnotch programs out there that regularly scan your computer for the presence of such problems – and that help guard against them, too. Buy one, install it and use it regularly; your crash issues may come to an end.
Possibility #4: Too Little Available Memory
When you buy a new computer, it feels like there’s no end to the amount of memory that it has. Of course, this isn’t true at all. As never-ending as the available memory on your PC may initially seem, the fact is that it can be depleted with incredible speed. You can find out for sure by checking the information within “My Computer.” If it appears that your available memory is low, you can use a PC cleanup program to remove unnecessary files; such programs remove things like temporary Internet files and other file debris that can suck away much-needed memory.
source:
http://www.computertips.com/pc-troubleshooting/