I've read a couple of threads whose OP's have the same problems as me, but their solutions to their problems seem to differ from mine. This place looks like a pro, so I decided i'll give this a try. Here:
A few days ago, I realised my D Drive (CD/DVD Drive) has disappeared! I don't know what happened, I didn't install Nero nor any Decrypter. I've had PowerISO all along, and I doubt it's the problem (but please tell me if PowerISO do cause any conflicts, so I can double check). I went into Device Manager and there wasn't any 'Secondary' or 'Primary' IDE Controllers for me to Uninstall and "let Windows sort out by itself". I've only got 3 'ATA Channel 0' ; 3 'ATA Channel 1' ; and 3 'Standard Dual PCI IDE Controller' - all under the 'IDE ATA/ATAPI Controllers'.
Another funny thing I realised is also i've now got a 'Floppy Disk Drive' - I don't have one in my CPU. How did it come about?