1)Do a monthly clean up. Each month, delete unneeded folders, and files. They take up useful memory, and if they become superfluous, can slow down your computer. If you're a pack rat and just can't seem to part with these files, save them to disk for future reference if needed.
2)Create system restore points regularly. Do this at least once a week. If weaker viruses are accidentally downloaded, the restore point will ensure that your data is recoverable.
3)Create backup disks. Backup any files that you use on a regular basis or files that are updated frequently. In the unfortunate event of a hard drive crash, you won't panic about lost work.
4)Use anti-spyware software. These programs can rid your computer of unwanted spyware, greyware, and malware.
5)Utilize anti-virus protection. If you can't afford an anti-virus program (or don't want one because of the negative effects it can have on your computer), simply conduct a free online virus scan. Two of the most trusted scans are TrendMicro (http://housecall.trendmicro.com) and AVG *one of my personal favorites* (http://www.avg.com/us-en/free-antivirus-download)
6)Perform a scan disk operation. Periodically perform a scan disk to make sure that your files are all in working order. This scan should be performed about once a week.
7)Defragment. Defragmenting your computer will guarantee that your files are organized and your computer is running at optimal speeds. This should be done at least once a month.
8)Consider formatting your hard drive. This should probably only be done if all of the above have been tried without success.
9)Stay away from websites that don't seem trustworthy this includes places like flash game sites, and blogs.
10)One of the most important of all is to always know your PC limits trying to fix issues with windows yourself isn't always the worlds most difficult thing to do, but keep in mind your data if your not comfortable messing with things in the windows registry, then taking your pc to a computer shop isn't only the smart thing to do it can also be the one thing that can make sure your data stays safe *You wouldn't attempt surgery on yourself*
Atricle is revised by mani with sources from personal experiance and open source documentation.