Does anyone know how to fix a Mac?

[The Skirata Clan]

I have been having issues with my Mac... Its an Intel based... The problem that I have been having its that its not regcognizing the startup disk... it dosen't find the Mac or the Windows partition on it... Apple tech support couldn't do anything with it... Geek Squad at Best Buy don't know anything about Macs... Which is really odd... two branches and either know nothing about Macs... The fans are working... however once it recognizes the disk it runs like new... diagnostics say the machine is perfect... I don't know what else to do...

Help me Obi-Wan Kenobi, your my only hope!