When ever I turn my computers internet on it Lags like hell but when I use my spare computer (the one I'm using now) the internet is fine.

What happens is that it continues to Acquire the network address and then connects for maybe 5 seconds then it disconects:( , saying the network cable is unplugged when it is. I've tried cleaning the ports and trying different cables and defrag sevrel times but when I do manage to make it work fine it does for about 12 hours then goes back to screwing up.:mad:. But this does not happen when I have the internet turned off so I'm thinking it might be the cause of software.

Any help would be appreciated because I'm going insane from the Lag it causes

Don't know about lag time, try ccleaner, it is a registery cleaner/optimizer
CCleaner - Home (http://www.ccleaner.com/)

Also
Try this,
Click on tools, internet options, connections tab and then click on LAN settings
Uncheck everything and click OK, try to get online again