Jaja, pl:

"After much looking into, I found that all drivers installed must support this function. The default drivers that come with Windows XP that automatically install your hardware during setup may allow your hardware to work, but they may not allow standby or hibernation. I had to go through each component and download/update to the latest drivers from the manufacturer. Turns out, it was my motherboard chipset driver that after I installed the latest driver, the Standby and Hibernation button during shutdown was no longer greyed out and was functional again."