Dell XPS Reinstallation CDs HELP!!!!

I have a XPS M140 w/ windows xp media center edition 2005 on it.  I recieved it in 2006 and I don't recall ever recieving the reinstalltion CDs for it.  And of course my warranty is expired now so I have to buy them.  I was just thinking of doing a PC restore but am afraid that this wont fix the problem I am having.  I had taken it to geek squad a few weeks ago to get a Webroot spysweeper program I had downloaded from their website off  (b/c i bought the actual webroot antivirus/spysweeper disc) and they couldnt get it off and wanted me to pay big bucks for them to check it.  They said it could be anything from a  virus or something wrong with my OS and that the most dramatic thing that they would have to do is reinstall my OS altogether.

So I was wondering if anyone could give me advice on what to do?  Will PC restore possibly help? or should I just buy my reinstalltion CDs from dell? And does anyone know a rough ballpark range of the cost of reinstallation cds?  Because I know I wont be able to purchase them at the moment and would like to get an idea of how much i need to save up to buy them...thanks so much!  Any advice would be greatly appreciated!!