No Standby button

i recently found that my stanby button is greyed out in the shutdown option.
My computer did use to standby before. all the settings are the same (im assuming), as my comp is set as Advanced Configuration and Power Interface (ACPI) PC.
Under "System Devices" there's even an "ACPI Fixed Feature Button" entry and a "MICROSOFT ACPI-Compliant System" entry.
Yet as mentioned the "stand by" button is greyed out in Start->Turn off Computer, and the "power options" control panel window doesn't have any standby/hibernate options.

WHAT I HAVE TRIED:
-system file checker
-reinstalling xp
...so far i've had no luck..can anyone help

 

Below info from MDGx Max Speed - Windows XP - Tweaks and Secrets - Part 1
Find this clip 4x paragraphs up from page bottom.

Please note portion in Purple and Orange print

HIBERNATE OPTION
Whenever you want to logoff, shut down or reboot your Windows XP machine you have only 3 choices (from left to right): (1) Standby [ONLY IF the ACPI/APM function is properly enabled BOTH in your motherboard's BIOS AND in WinXP!], (2) Restart and (3) Shutdown.

To properly enable Hibernation in WinXP: Start button -> Control Panel -> Power Options -> Hibernate tab -> check Enable hibernate support box -> Apply/OK -> reboot.
NOTE: If the Hibernate tab is unavailable your computer does NOT support it!

For some reason Microsoft did NOT enable the 4th option: (4) Hibernate, which should be available on power saving (ACPI) enabled PCs and laptops.
But you CAN bring it back: just hold the Shift key while the Shut down menu is displayed on your screen, and notice the Standby button being replaced by a new, fully functional Hibernate button, which can be clicked with the left button of your mouse.
If you release the Shift key, the Hibernate option will disappear once again, to be replaced by Standby. Hocus-pocus!

 

ermmm...thanks for helping but i tried all of that stuff already....no luck..

its not a h/w problem either as i was able to install xp on a different hdd..

 

If you have previously checked BIOS settings and tried "hold the Shift key at Shut down menu ", don't have anymore specific suggestions. I see you have joined in wBBS post, Standby Problems. Hopefully the thread starter will share his solution.
Good Luck