Reseted BIOS, now Windows/Linux won't start!

Hello,
I'm a noob and I should never mess with my computer ever again (just a short mental note I should remember).
Anyway, I overclocked my computer to 2.7 Ghz (I got Intel 2.4 processor) and it worked fine. Then, when I overclocked it to max (3 Ghz or more, dunno how much was it) and when I turned on computer, I got blank screen on my monitor and long beep (probably for overheating).
I read on the forums how to fix the problem and I did reset BIOS using jumper and I could get into BIOS, clock was back to normal.
The problem is that I can't start my Windows nor Linux. When I try to boot Windows, I get nothing, just a black screen (and I got restart once) and when I try to boot Linux i get message: - - System halted.
I removed CMOS battery to reset BIOS (or whatever the hell that battery is for) and nothing changed.
Also, I tried to re-install Windows by inserting Windows disk into my CD-ROM and installation booted but it got frozen and I had to restart computer.
I have no idea what to do! Any help will do :)