I only know a few tidbits for stuff like this.
You can start with a copy of "dumppo". It's a small utility (13,072 bytes)
that runs in a command window.
ftp://ftp.microsoft.com/Products/Oemtest/v1.1/WOSTest/Tools/Acpi/dumppo.exe
If I run this command
dumppo cap
I get a line like this
System states supported.: S1 S3 S4 S5
S3 is suspend to RAM, while S4 is hibernate.
That state list, can be affected by the BIOS. You might find references
to S1, S1&S3 in the BIOS or the like. Changing the BIOS setting, can
prevent Windows from using the ACPI states denied by the BIOS. Sometimes,
something as simple as replacing the CMOS battery, can result in a loss
of full ACPI functionality.
Wow, dummpo is great. I got:
E:\Downloads-ShouldBeXP>dumppo
dumppo: cap ps bs admin ac dc
E:\Downloads-ShouldBeXP>dumppo cap
power capabilties
System power capabilties
Power Button Present....: TRUE
Sleep Button Present....: TRUE
Lid Present.............: FALSE
System states supported.: S1 S4 S5
Hiber file reserved.....: TRUE
Thermal control.........: FALSE
CPU Throttle control....: TRUE
Processor min throttle..: 7
Processor trottle scale.: 100 (1%)
Some disk will spindown.: TRUE
System batteries present: FALSE
System batteries scale..: (G:0 C:0) (G:0 C:0) (G:0 C:0)
Ac on line wake ability.: Unspecified
Lid wake ability........: Unspecified
RTC wake ability........: S4 - hibernate
Min device wake.........: Unspecified
Default low latency wake: Unspecified
There are about 7 things up there that I didn't know, and about my own
computer. Now I just have to find out what they mean! If I can't
find it out by reading, I'll tell you which ones they are.
I will note that I'm missing s2 and s3! But stand-by and hibernate
work, so they must be other s numbers
Once you correct the BIOS setting, you can use "dumppo" to do an
"administrative override" and fix the list. There is an example
of doing that here.
http://forums.pcper.com/showthread.php?p=1825058&postcount=31
Good reading!