Why is my computer sometimes gets very slow?

like my internet goes slow and everything goes slow. i know is not because of the prgram i install. There is no virus on my computer. but i did install skybot and anti-virus protection. What's the reason why my computer gets slow? What should i do to change? i was wondering to buy new graphic card, but there might be another reason why my computer is slow.

here is my computer detail

512 ram

windows xp pentium 4

ati radeon 9250

1.60GHz

plz tell me what i should change i do not want to buy another computer.

Why is my computer sometimes gets very slow?ariel

There are several primary reasons could cause your computer to be slow and also some softwares you can download to speed up it.

First,Corruption and Errors within your registry.The registry is a main part of your computer's Operating System. With time, as you use Windows and install and uninstall programs, your registry will get congested and full of errors. So your computer could slow down. So, if you can clean it up this problem can be solved.Sometimes you can speed computer up by 300%. To clean up registry,You can download a software called regsitry cleaner---Clean registry,remnant,corrupt files and temp files,history,cookies,etc.. This site:

http://fix-slow-computer.info

lists top 5 registry cleaner,you can download and scan for free.

Second,Your computer is loaded with spyware/adware.spyware/adware hamper your computer's performance.It use system resources and slow your computer down.