Win 7 crashes when installing new software, everytime

Back story: two year old nephew hits the power button while I was browsing the net. Nothing out of the ordinary with it. However, since then everything has gone to batshit crazy. First ChromePlus, a browser, goes bad. It would freeze Windows the moment i launched it. I deleted that and things seemed to return to normal. Then the exact same problem happened to MSN Messenger.

So i deleted MSN messenger as well. And the PC is running perfectly fine, However, whenever I try to install something, anything for that matter, Windows crashes and eventually gives me a BSOD.

It seems it has locked itself. I have no idea what's causing it. I wouldn't like to reformat and I am hoping there is a solution to this. Unfortunately, for some reason, there was no system restore point! So can't do that as well. I am really hoping some of geniuses have an answer.

System:
i5 750 @default
4GB of RAM
GTX 570
60GB SSD (Windows)
250GB HDD (general).

Try to run this command sfc / scannow, httwww.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

I did that. It say it found some corruption but wasn't able to fix them.

Bumping.

Following my issues, I formatted my PC. The PC ran fine for two days - i installed softwares, games, and watched couple of movies, and everything was just fine. But suddenly last night, it started crashing again.

CHKDSK fails. Rebooting from crash saying no boot device found. System restore didn't help either.

I am not sure what's the problem. Maybe the HD? But why would it run fine for two days and then error out so suddenly?

Any help would be appreciated.