and the magic solution is: (if using IE, I haven't played much with Firefox yet)
- a decent (and regularly updated) antivirus program, such as Norton or VET
- Ad-Aware SE
- Spybot - Search and Destroy
- Javacools SpywareBlaster (a semi-sponsored/semi-addon for Spybot)
- the Google toolbar, with an inbuilt popup blocker (which can sometimes be TOO effective, but allows permissions to be set for individual sites)
these are available from Download.com, or just use Google.
- stop searching for downloadable retail games/movies - by the time you've found what you're looking for, you've downloaded enough crap to fill twice the hard drive space.
- ease up on the porn... (or just use P2P
)
This process has served me well for quite a while now - even when other family members inadvertantly install some sort of commercial shite, or at work, when the manager's son jumps on the business email terminal and goes nuts with the Cartoon Network and WildTangent programs.
If you're still having problems, it's time to learn how to dig around in the registry...