There are few things which you can do to maintain your personal computer.

Click http://www.bobfishersays.com/computers/ten-tips-to-keep-computer-running-smoothly.html for 10 Ten Tips To Keep Computer Running Smoothly.

Other things you can do is Virus scan your computer from time to time. There are many virus checker programs on the internet. There are many for free.

Goto www.download.com and search for Virus checker.
AVG Virus checker is a great free one it also includes the Spy Ware checker program.

Also download the program AVG Spyware or Ad-aware or an equivalent program to check your computer reguallay. A major problem found today is Adwerts or Spyware programs get inside of computer which slow your computer down increadable. Spyware software are similar to vircuses except a lot of the time there are not there to destroy your computer, just scan for password etc and it really does slow the computer down.

Make sure if using the internet and your browsing that you never download or say YES to anything unless you requested and you know what it is. Even if the message says it is safe. For example there are Spyware software which is on the web which says it is from  Microsoft and it looks legitament but it is not. So unless you are a Microsoft Website or partner do not accept these type of messages unless you are sure.

There are even emails pretenting like are from PayPal or HSBC bank but are fake and are only intending to get passwords or grater off you.