My laptop (thinkpad x61) have been unable to standby for sometime. It used to work fine. I googled a lot and failed to find a solution.
The symptom:
1, Power button or start->shutdown, the menu shows: greyed Standby (press shift will not switch it to Hibernate), Shutdown and Restart. But if I do it before user login, the Standby button is normal and Standby actually works, yet only once, after back from standby, it becomes grey again.
2, Control panel -> Power options, there is no Hibernation tab; but in Advanced tab ->close the lid, there are two options: Do nothing and Hibernate, without Standby. Closing the lid will make the screen dark when Do nothing is chosen.
3, Cmd -> "powercfg /a" gives: The following sleep states are not available on this system: Standby (S1) Standby (S2) Standby (S3) Hibernate.
4, Under C:\ there is hiberfil.sys, which cannot be deleted. Even if I deleted it after closed the file handle by procexp, it recreates after reboot.
5, In Lenovo's power management software, "Enable hibernation" is greyed out.
I have reinstalled Intel chips driver, Intel video driver, ACPI driver, power management software; checked BIOS, nothing relevant. Switched memory from 4G to 2G; stopped services and killed processes one by one, while checking the shutdown Standby menu, still grey. Group policy has no relevant option either. The last thing I won't try is reinstalling Windows.
I think maybe Windows is given the false information about sleep ability after user logged in. Is this information hidden somewhere in the registry? Any suggestion is appreciated.