If you've read any of my other posts, I just got a new video card. Upon further exploration, I am unable to have my system enter standby or hibernate modes. The Hibernate tab in power options is gone, so I can't enable hibernate.

Did you recently installed/reinstalled windows ? Did hibernate/standby worked before ? Assuming you are using windows xp, check ACPI support is installed, go to ctrl panel > system > hardware > device manager > expand 'computer'. The entry should be something like 'Advanced configuration and power interface'.

After installing the new video card, you also may need to install updated drivers for it. http://www.microsoft.com/WindowsXP/pro/using/tips/maintain/nostandby.asp

It has to be enabled in the BIOS Setup.
In mine the settings are:
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"Power Management Setup Menu"
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"Power Management : User Define"
"PM Control of APM : Yes"

Bofore I set "User Define" mine wouldn't work either.
[It used to be "Disabled"]