You have a drive with a primary partition without boot code in your boot order. This is usually a forgotten external drive and for some reason the loader will not just skip it. This is the only time, that I am aware of, that the word "operation" instead of "operating" comes up.
Thanks Jim C for your reply.
I tried to fix that by installing fresh using my recovery disk. But it didn't work... So considering problem with hard-disk, I thought to start laptop with another hard disk. I have another laptop Dell studio. I replaced hard disk from Dell studio to Dell XPS... And started system. It worked and was working fine and smoothly...... My laptop warranty expired.. So don't know whether it has diff warranty for hard disk or hard disk warranty(Toshiba 640GB SATA) is also expired with the system.
Finally I will buy out new internal hard disk, and try out my luck And let you all know whether it solved my problem or not.
The hard drive that came with the system carries only the system warranty - nothing else. And with Toshiba, getting support on even drives purchased separately can be an experience -- unlike WD and Seagate, they generally don't provide much end-user consumer support for drives.
I bought new HDD 500GB, and installed Windows 7 Home Premium again. and Now my laptop is working fine. I have restarted it many times and updated many fixes online. It has solved both the issues "Operation system not found" as well as freezing issue after typing. I think it was due to HDD problem. Due to bad sectors or bad boot sector or other issue it was not working well, Even while shutting down the laptop, just before power off it was giving some sound from HDD look like when you do Hard reboot of a PC by pressing the power button.
All is well in the End I am writing this post from same working laptop !!!