correct me if i got any of this wrong....
your moms comp... starts up fine, it beeps, and you can see the BIOS Post screen(or Manufacterer Logo) but once windows starts loading it instantly locks up and no display is shown.....
IF so, then theres only 2 likely possibilityes....
) your Harddrive
) or your System Ram
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you can easily test your Ram, by downloading Memtest86(pre-compiled-package-for-floppy), extract it to flopppy disk, and boot from the Floppy. (it will auto run on Boot).
download from:
http://www.memtest.org/#downiso
note: it continually tests the ram for an infinate time limit, just Hit Escape whenever it finishes with a PASS.
you can Download Diagnostic Utilityes for boot floppy to test your HDD, for Free... HDD manufacturers always have such utilities on there Support/download section of there website.
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But first.... when you guys Re-Intsalled windows... during the installation did it give you a warning similar to: "waning the option you chosen will erase all data on your harddrive"
because if it didnt, that may mean you may have done a Repair install or a Install over your Old OS, witch wont work correctly. note - A clean install will Reformat the Harddrive.
also you can check simple things such as: *If you moved anything inside the case(if not ignore this): check to make shur all your harddrive connections are tight/proper.. and the Jumper Setting on the HDD is correct.