BSOD And Arrow Keys Not Working?

A week back or so, it was all fine (With occasional Win 7 freezes, which i have never been able to troubleshoot). Then my Win 7 started showing a BSOD (Pretty frequently but randomly). While struggling with this i tried to add/remove RAM sticks (I am running on 4* 2GB = 8 GB in total. Tried to keep one stick (changed slots as well) and remove other three but still the same BSOD). Then i removed NVIDIA graphics card, hard disk & CD rom cables, processes and put everything back again. But to no use.BSOD was not really an issue, as I was thinking of reinstalling Windows and getting rid of that. Before that while Windows would restart (after a BSOD) the arrow keys were not working means: i was not able to choose from 1) boot windows normally 2) run repair etc options.Then i thought of booting the system from a bootable USB drive and run the repair. I pressed F12 to choose one time boot device, it showed the list but arrow keys were not working again. Strangely enough if i enter BIOS setup by pressing DEL, everything seems to work fine. So finally i made the USB drive my first boot device and the system was able to boot from it.I also had one Acronis bootable CD which i used for creating an image of C drive (After fresh Win 7 installation). I thought about restoring that image. I set my first boot device as CD ROM and was able to boot into Acronis. It gives 2 options (the default being boot into Windows). Acronis is a GUI based stuff so i tried to use mouse there. Oh man now mouse was not working and following the default option, the system was booting into Windows.