Comp crash help!!!

[GrungyHobo]

My comp was on running fine i left for a while i come back and the comp had crashed and was on a screen that was talking about can't find the A drive. I restarted the computer and it wont start b/c A drive is missing, iwent into bios and turned the a drive off and restarted. Comp loaded windows but everything in vista turned off and then it crashed again. I restarted and windows failed to load screen came up. i then restarted with the vista disk in. vista copied files or loaded them as soon as it finished the can't load vista came up again(it says a hardware change/failure or configuration change won't allow vista to run). Also i tried to start vista in the last configuration that worked and that failed.
I went to geek squad they said my HD probably failed and I need a new one, but they want $70 to run a diagnostic test to find out. So my question is 1. do you think they are right about the HD? and 2. how can i run a diagnostic test so i don't have to pay $70?
PLEASE HELP ME

 

[LA1]

every hard drive manufacturer has FREE diagnostic software you can download. Some are really comprehensive including data migration. Some will diagnose other manufacturers hard drives. I know that western digitals will diagnose some other brands.

 

[Dystopia]

Which drive IS the A drive? If it is your hard drive, then start with opening up our computer, reseat the cable at both, the mobo and the hard drive, then do the same for your power to your hard drive. If that doesn't fix it, buy a new hard drive (from newegg if you are in the USA, Canada, or China) and test it. Try loading vista, the whole 9 yards. IF that doesn't fix (which I think it will) then you can return the hard drive, just tell them it didn't do what it was supposed to do, and done.