Sir,
My computer boots up to the windows screen where you have a dot scrolling horizontally and then it restarts with a beep.
Please help.

Hi pawan,

There are couple of reasons responsible for same... drivers or power supply.

Easiest thing - can you boot into safe mode? IF so, reinstall chipset drivers.

If not , let me know, I will guide you further.

Also, I please tell what you did when you last time installed the computer.
Did you opened the cabinet and did something inside?

This can also be caused by a bad CPU or a bad chip on the motherboard. This requires a CPU or a mother board replacement.

If you can't boot into safe mode, you can check the power supply with a voltmeter. Check for ripple by putting the voltmeter on the AC scale. There should be virtually no ripple. If there is, you can replace the power supply. Here are some pin-outs for various power supplies.

ATX, BTX, WTX and other power supply cables connectors pinouts listing

If you have a voltmeter, but aren't sure how to do this, repost and I'll give you more information.

Dear Libran
Thanks a lot for your advice on my problem. The fact is I can't boot into Safe Mode. If I try booting in using Safe Mode, the computer gets stuck at some point and then restarts. As to whether I did something inside the cabinet, well, I am just back after summer vacations and somebody else might have been up to something. I am not sure about it.
Please help.
Thanks.
Pawan

Assuming your using XP, first thing you should do is try running chkdsk. If you have your Operating System (XP) disk put that in and boot to it. The first screen will come up and then just hit R to run a repair.

It will go to a black screen, just let it time out, it's only like 4 or 5 seconds. Now all you have to do is select the C: drive by hitting 1 or whatever number is next to it. Then it will ask you for an Administrators Password, just hit hit enter. 99% of the time there is no password. Then you will come to the C:\. All you have to do is type chkdsk /p then hit enter. Do it as many times as you need to until it comes back with no errors found.

I hope this fixes your problem!

Hey most probable reason is your SMPS is not working(its burnt or something) Check that