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.
All this leaves me with heck lot of frustration and i am not able the figure out where the issue could be. As the warranty of the system is going to expire, i would like to check with the hardware vendor (with a hope that he would be able to figure out something) as soon as possible, if it looks like to be a hardware related issue.