OK I have trouble shooted many computers in the past.. There are many questions and problems that could be a problem but let's start with what is the most common..

First of all you gave very basic information so...

Is the desktop connected wireless as well or hardwire ?
I realize most people hardwire desktops in, but there are exceptions and this is very important..

What OS ( Windows, Linux or MAC ) version is it running ?

Does the Desktop have a Firewall on it and did you try turning it off ? ( Sometimes it must be removed )

Does the Desktop have Antivirus on it ?

If the Desktop is connected hardwire, does it show network connection and proper network settings ?

OK if I lost you anywhere I tried.. http://www.discussworldissues.com/fo...illy_nilly.gif

Run the antivirus program and it will be fixed.

Desktop
 

So the internet has been cutting in and out, when I restart it the internet is fine for about five minutes, then it stops working. The modem is fine and the router works great. My dad and I can access the wireless internet with our laptops but for whatever reason the desktop can't... :/ I need that computer to do my online school work as I can't do it on either of the laptops.

Sheesh, thought you Americans were immune to technological breakdown

It's not even connected to the internet?

hmmm....any weather problems?