Wireless desktop can't connect to internet while laptop can

Hello, I have not been able to access the internet from my wireless desktop. I have a desktop hardwired to my router (frontier(ISP) provided) and we can connect w/ our wireless laptop and visitors can connect w/ their personal devices. The wireless desktop was taken to the shop for removal of the usual virus, malware etc. and I can see that they were able to connect to the internet because the norton program was updated. The wireless desk top shows a very good connection to the frontier modem but I cannot reach any sites. The repaire shop says that it's a router problem and frontier says that as long as I am showing a good connection to the router, it's a computer problem. The repair shop said that they could come out to fix it w/ travel time we would be looking at about $300.00 on top of the cost for the clean-up. The system is set up for a linksys connection (router) but frontier say's that that should not matter.
ANY ideas would be helpful.
Thanks