Alright the reason you get NTLDR is missing cause you changed your hardwaer configuration. Switching out the CD ROM drives changed your config from the one you installed Windows with. That error can be fixed easily. But you need to copy that file from windows to a Flash drive or CD or something. Or visit this site:
Troubleshooting Windows XP - NeoSmart Technologies Wiki
Download a copy of it and paste it to your boot drive. Can use a LiveCD to do that.
As for the VGA you are encountering that file needs to be replaced still. But since it seems your CD ROM drive is going that wont happen. What corrupt files does it say it is missing?
Your best option might be to put n the other CD ROM drive and doa repair install.