OK, thanks - I forgot about some PC manufacturers and their recovery drives, hehe. I have a recovery partition on my Dell, but I also received a full Vista Home Premium 32bit DVD.
So, booting from an OS disc is out.
What software are you using to try and play back your DVDs? Might be worth a shot to install VLC player and see if that helps.
I’m guessing since you removed the drive from the PC to clean it, that all the SATA/power cables are plugged in snugly.
If all else fails, any chance you or a friend have another PC that you can try the drive inside?