Run the Dell Diagnostics with the extended hard drive test. Your hard drive might have failed.

If you hit F1, does it boot normally?  (I'm assuming not, but there was no mention.)  Whether it does or not can give a hint as to what the problem is.

What color are the 4 diagnostic LEDs on rear of the tower?

Ron

I hear the cdrom trying to run, but the message comes up again and again

Mary G
how can i run hard drive test ? anyway , i´ve connected the hardisk to another computer and tried to move files to and from . there seems nothing wrong with it

RoHe
they are all green

theflash1932
the same message comes up when i hit F1 key but it takes longer when I put the disc I hear the cdrom trying to run, but the message comes up again and again

If you have more than one optical drive, try the XP CD in the other drive.

Try booting from your Dell Utilities CD. If that boots, then your XP CD may be damaged. The hard drive diagnostics should be on the Dell Utilities disk.

The drive may be physically ok, but if the boot sector or master boot record are corrupted, it won't boot.

Reboot and press F2 when prompted to open BIOS setup. Look under Options for Primary Hard Drive 0. Make sure it's recognizing your hard drive correctly and it's set to AUTO.

Ron

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i wanna ask , can i setup windows from USB stick on this computer DEll dimenition 8250??
i mean that is no option USB on the boot sequence list

se this img
http://img7.imageshack.us/img7/5066/dsc00610mj.jpg

or another way , if i copy setup files to the hard , can i boot from it ??