Geek Squad "techs" are more salesmen than any other staff in the store. They're more interested in the upsell than really fixing your problem.
If you're not up for upgrading then they'll keep your PC for a day or two to run diagnostics and such before telling you that your hard drive is bad. Then charging you about $180 for all of that, as was the case with one of my friends.
After paying me with a case of brew, I ran a chkdsk /r on his PC and had the problem fixed in an hour.