|I have added more to response 2 - please read that.|
"The Laptop is a Compac nc6220
I dont know keys wich brings out the cdrom or the recovery partition if it has one"
"Most laptops display a line while booting "Press (a key) for Boot Device" or similar."
If you don't see that, go to the HP website and look at the Owner's or User's manual in the software downloads for your specific model . That manual probably also has Recovery info in it. Most Compaq computers I've come across that had XP installed on them originally came with an XP re-installation CD or similar and in that case they DID NOT have a Recovery partition on the hard drive. The Owner's or User's manual Recovery procedure will probably tell you which situation is your case.
"tried disconnecting the CMOS battery for 24 hours, the date is outdated but it still require a admin password"
The password info on modern laptops is NOT stored on the Cmos part of the bios chip - "The passwords that are set in the bios of modern laptops are stored on a chip other than the bios chip that is soldered into the mboard and that cannot have the user settings erased from it by removing the power to it. "
You don't have a system access password (must be supplied to use the computer at all) you don't know, because if you didn't know it you would not be able to even try getting into the bios Setup.
"ang the OS on my harddisk is corrupted,even after pressing F8 for safemode doest help"
Are you getting a message on a blue screen ?
If yes quote what it says.
Have you tried selecting Disable automatic restart... when you pressed F8 while booting ?
A common reason for corrupted data on the hard drive is the hard drive is in the process of failing.
You should test the hard drive before doing anything else.
Test your hard drive with hard drive manufacturer's diagnostics.
Seagate's SeaTools will test (almost) any brand of hard drive.
Do the long test.
The Dos bootable versions of SeaTools can test the hard drive when Windows will not load properly, or even when the drive has no data on it.
It the drive itself passes the test, any data problems on the drive can be fixed one way or another.