Congrats on the venture! More and more of us are working on things to bring in a little money, it seems. This is what I've been up to Good Kharma Tags, and my Facebook page: Good Kharma Tags - Local Business - Morristown, Tennessee | Facebook
Oh I know that feeling all so well...been there, wrecked several PC's before I got good at fixing them, lol. Maybe you know someone with an external CD ROM drive that would let you borrow it to plug and play to reinstall? This problem intrigues me, I wish you lived closer so I could look at it. You can actually buy an external DVD drive for about $40 (still cheaper than a shop) plug it in, and then go into the BIOS and tell the PC to boot from it to do your reinstall. They're also kind of handy to have anyway and it doesn't have to be super fast to work.
You're right, a computer shop is going to charge you big time and it will probably take them 30 minutes to fix it, maybe an hour if they wait for windows to install.
Ok so it's from deleting something? Maybe a simple fix! When you boot up and hit like F8 to get the screen that shows you "safe mode" etc - try hitting last known good configuration. OR alternatively, go to windows and have it skip back to a previous save. Last known good configuration usually works but going to system restore might also fix the problem if you go back far enough.
My email said it never sent, lol - so I sent it a 3rd time as well. I know something else you can do to reinstall windows though without using your CD ROM drive. Have another computer? Burn an ISO copy of windows onto say a jump drive or external HD, along with a program like Daemon Tools (don't use if you have Win 7, it doesn't work) or Magic ISO. Magic ISO runs like another driver but it's a "fake" drive - emulator. You can load windows ISO files from the emulator on the external drive to do a repair - which would hopefully fix it well enough to get your CD ROM drive back to being functional and where you could format your HD and start over.