Goto your router settings find * Services* or something along those lines, Basicly where it tells you all the pc`s connected to your router, You then select your host pc and edit the settings there should be a tick box that allows you to make that ip address static for that machine. Thats all you need to do if your running vista.
If your on XP it may be slightly harder, goto run > cmd > ipconfig /all then goto network connections, local area connection right click, props select tcp ip you then need to fill out the details from the cmd window, It should tell you everything you need to edit. Then hit applly and ok
Thats just a quick off the top of my head guide, So sorry about the lack of detail but it should give you a rough idea on how to go about doing this.
If all esle fails search your best friend, Youtube for a video explination.
Good Luck
/Zen2
