|If the video adapter is a card in a mboard slot....|
Unplug the case/power supply, or switch off the AC power to it otherwise.
Power off your monitor.
iOpen up the case by removing the left side panel as seen when you're looking at the front of the case.
Make sure the video card is all the way down in it's slot.
If it has a fan, examine it to see if it and/or it's heat sink is clogged with mung, and if it is remove the mung but DO NOT use a vacuum cleaner to do that (see below) !
If it has a fan, temporarily connect the AC power to the case, boot the computer, and make sure the video card fan (and cpu fan) spins okay.
While you're in there, if the cpu fan/heatsink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. It may be difficult to clean the top of the heatsink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
If you have re-loaded Windows from scratch, Standby or Hibernate mode may not work properly until you have loaded the main chipset drivers, which include the ACPI info Windows needs to know about - how Standby, Hibernate, and Re-start are supported by the mboard.
Whenever you load Windows from a regular Windows CD (or DVD) from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, in order for Windows to have the proper drivers for and information about your mboard hardware, including it's AGP or PCI-E, ACPI, USB 2.0 if it has it, and hard drive controller support. If you have a generic system and have the CD that came with the mboard, all the necessary drivers are on it. If you load drivers from the web, brand name system builders and mboard makers often DO NOT have the main chipset drivers listed in the downloads for your model - in that case you must go to the maker of the main chipset's web site, get the drivers, and load them.
Load the main chipset drivers first.