Bios has got nothing to do with it...
Registry goof ups don't alter hardware bios settings.
System restore will not "restore" all your computer settings. System restore is not to be used as a backup tool for your PC. In extremely many cases it does more harm then good.
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Here is some chat between me and mwe99 about this, prior to creating this thread. It contains some (possible) things to do/try. It isn't that accurate or well explained though, hence not something I like to post to a forum, but anyways...
quote:
Via MSN Messenger chat
mwe99 says:
hey you busy?
me says:
not really but I'm just home and wanted to watch some TV for what time is left before going to bed
mwe99 says:
lol
nooo
stay for 2 secs
my friend needs some help
me says:
shoot
mwe99 says:
He installed something and it ruined his drives I think
me says:
? drives aren't that easly "ruined"...
mwe99 says:
Totally lOst thread..
me says:
unless he program involved things like formatting and "fixing" low-level stuff of course
mwe99 says:
see the thread?
me says:
not much time to research it... but tell him to start by removing his DVD/CD ROM players from the PC, then restart (so windows really doesn't reconize them anymore as they are not installed), remove any left-overs from unused drivers (thus, those from the dvd/cdrom drives) the proper way, turn pc off, reinstall dvd/cdrom drives, reboot, reinstall drivers
And also don't let him forget to reinstall anything else (from drivers to settings the correct things back) since the time the system restore he used was saved...
me says:
also let him check the hardware tab in his system config panel
me says:
if windows reconizes his drives again and they perform in the proper way with other stuff, let him surf to the official C&C's website and let him check for updates and/or fixes or whatever...
Tell him not to mess with registry just like that if he doesn't have the knowledge only because "a friend said so"... (and certainly not without first taking a backup of the registry) 
mwe99 says:
Thanks
me says:
among the common bugs (which will have official fixes) the message "Cannot locate the DVD-ROM" might also simply indicate a bad/corrupted/scratch/whatever DVD disc...
mwe99 says:
Post cos I’m not on my pc lol
me says:
it even can be that the other games he is talking about, need a special kind of installation or another installation (eg: on hard disk) than the main games... let him (re)read every piece of documentation that comes with the discs and/or games
/ 
