Wired or wireless?
If wired: ethernet cable or power line adapter? Direct to router or via wall outlets?
Who has admin rights to your router?
Are you using a USB to ethernet adapter, a PCI-x ethernet adapter, or a built in motherboard adapter?
If wired (in any manner) try connecting another computer - see if problem affects that computer.
Try connecting your desktop somewhere else. See if the problem follows the desktop.
Need to narrow things down.