There have been a lot of systems hi-jacked by fake anti-virus/anti-spyware/anti-malware programs lately.  You can do a lot to avoid these and other malware.

Do not install anything unless it is really needed and is from a trusted source.
Use a non-administrator account as your main account.  

Here are some simple rules to follow to keep Windows running smoothly: keep it updated, keep it simple, keep a backup…

Keep windows updated. Don’t ignore that little yellow or red shield down by the clock.
Install an anti-virus program, keep it updated, and

Spyware causes as many, if not more, problems on computers as viruses do. But spyware can often causes no problems at all (the best spies are the ones you do not see…). Find spyware and get rid of it using a program like Malwarebytes’ Anti-Malware (www.malwarebytes.org) or Ad-Aware (www.lavasoftusa.com). Avoid getting spyware in [...]

A good anti-virus program is still important for keeping Windows computers running smoothly. There are many good ones, but few that offer as much protection as they were able to a few years ago (malware writers have the advantage lately), but NOD32 seems to be one of the best (www.eset.com). And for home [...]

If it is too hot for you, it is probably too hot for your computer. Turn on the AC or turn off the computer. Hibernating a Windows computer or putting a Mac to sleep is also fine!