this cd that im using is a pirated one.. but i've already used it many times without error.
Like my TV worked every night for 10 years, so why won't it come on now?
When people say things like that it always reminds me of the mandatory advice that has to be printed on advertisements for investment products in the UK, "past performance is no guarantee of future results".
"Used it many times" could mean "scratched it many times".
You could have a hardware problem, possibly RAM related.
Also, going the illegal route could cause you problems.
New brand-name computers (Dell, HP, Gateway, etc.) come with Windows XP preloaded that has an (Original Equipment Manufacturer) OEM licence. The OEM licensing system is different to that of the retail packaged version of Windows XP. The OEM licence does not allow Windows XP to be transferred to a new computer; the retail licence does allow such a transfer. OEM copies are only licensed for use on the new computer on which they were originally installed.
Many OEM copies installed by the major manufacturers (Dell, HP, Packard Bell, etc.) use a system called System Locked Pre-Installation (SLP) that doesn't match any hardware on start-up. It looks for a special signature in the BIOS setup program instead. If the computer's installation Windows XP has a file called oembios.bin, then it has SLP-activated OEM copy.
If a BIOS-locked copy of Windows XP is installed on a motherboard and the BIOS lock fails, the system will go through the normal Product Activation process at startup. However, note well that from March 1, 2005, the Product Key supplied on a label by the computer manufacturer, and used for the initial installation, won't be accepted for activation. A new copy of Windows XP, with a licence allowing installation on a different computer, will be needed. This means that any replacement motherboard, or upgrade to its BIOS, must be supplied by the original manufacturer in order to ensure that the BIOS lock is put into effect.