i was juts doing things and then my machine rebooted i tried to start windows again but get some kind of a scan disk program... it scanned my hard disk and found nothing iteresting then booted... next time i desided to skip that scan but it re booteted.... 3rd time i let it do the complete scan it found some thing and fixed them and rebooteted..... now my system is starting normaly but it reboots just before loging screen appears.... so please help me if you can... i need your help PS. i dont want to re install windows becouse teh i would have to install every thing again...

Maybe this???

Windows XP Logon Screen Does not Appear and the Computer Continuously Restarts

http://support.microsoft.com/default.aspx?scid=kb;en-us;310396

i would just reinstall windows xp again if you go to www.bootdisk.com you can download a boot disk make sure its for xp home im assuming you have the windows cd disc. just follow the instructions

A repair install will not make you have to reinstall everything.
You will not lose much.
If the page Chuck gave you doesn't work or apply, try a repair install.
The procces is the same for both windows xp home and xp pro.

(NOTE: you will lose all restore points when you do this as well as you lose your old registry backup from the c:\windows\repair folder as it will create a new backup to replace it. If you rename the repair folder you wont lose that backup, but you will still lose the restore points)

To perform an in-place upgrade of Windows XP: (thats what they call a repair install)

1. Insert the Windows XP Setup CD-ROM into the CD-ROM drive, start the computer,
and then press ENTER to select the first option screen to install a copy of
Windows XP.

2. Click Accept.

3. Setup detects your installation.

NOTE: If Setup does not detect a previous installation but continues to the
partitioning window, there is a problem. An in-place upgrade may not be
possible on your computer.

4. When you are prompted to repair the existing Windows XP installation, press
R. Windows XP Setup performs an in-place upgrade of the existing
installation. Note that you might lose some of your customized settings.

hope this helps

You can also use a WIN98 boot disk; click "Yes" to "Start With CDROM Support". after it gets done loading the virtual drivers, at the DOS prompt switch to the CDROM drive letter (usually E), type SETUP.EXE and XP will launch (have the XP disk in the ROM, of course).

Sounds suspiciously like a failing HD. Sudden scandisks, not following a crash in windows, are a bad sign.

Testing the HD with the manufacturer's diagnostic software would be a good idea.