Hey mate, sounds like they just wipe the hard drives clean meaning you have to reinstall windows. If you want to test if the hard drives have any physical problems crack open the side of the case and look at what brand the hard drives are and if they have a flat wide cable or a thin roundish cable. Then type in the manufacturer name e.g. seagate go to the support section and download the hard drive test cd. It will be in a format called iso you then use nero to burn this "image" into a cd and boot from the cd.
When I worked for govt we used a program to wipe the hard drive all data prior to sale. This is due to the privacy act. It doesn't do anything as such to the hard drive. If your cpu was stuffed when you booted the computer you wouldn't get anything on the screen and the computer would most likley beep.
To get into bios switch on the computer and it will say press F2 F8 or Del (Delete) to load setup. This is the bios screen (basic input output system) if you can get to that then your cpu is fine. To test if the memory is ok you can download a program called memtest from here
http://www.memtest.org/download/1.70/memtest86+-1.70.iso.zip you need to let it run for 24 hours but if there is an errror it will find one. If you get online sometime when I'm on I can help walk you through some of this stuff.
Anyone is welcome to correct anything I have said that is wrong.
