Overwrite One Copy Of Windows 7 With Another?

My laptop decides to refuse to power on. Not just boot, the power button had no response. 3 months later, i finally find a cheap motherboard for it, and swap it out.In that 3 months, i had taken the hard drive out, and had used it as a slave drive in my family's desktop. I'd occasionally boot directly to the drive itself, and after the first boot, it automatically obtained all the drivers for the desktop. All was well.

Well, about a week before my motherboard arrived, Windows 7 freaked and reset the permissions for every one of the 401,541 files on the partition during a scheduled chkdsk (replacing invalid security ID with default security ID). Now, it'll boot, but after the "Windows Loading" animation, it'll give me a black screen and a cursor. Nothing more. no key combinations (so no replacing sethc.exe with cmd.exe), no nothing. I can move the cursor, and turn the computer off.