|There are several common causes for that.|
- you have reloaded Windows from scratch but you haven't loaded the main chipset "drivers" after Setup was finished. Windows needs info included along with the main chipset "drivers" in order for it to know how the ACPI features of your mboard, including Standby and Hibernate modes, are supported.
XP doesn't have the drivers built in for most things that first came out after XP was first released, circa 2001, and it doesn't have some of the drivers built in for things made before that.
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.
- you have a problem with your built in display, or you have a problem with your main battery or the charging system for it (I'm assuming this happened when the AC adapter WAS plugged in) :
Laptop no video (or video problems), and battery, AC adapter, power jack T shooting.
See response 1:
DO NOT plug in or unplug a monitor's video cable into / from a video port while the computer is running. Doing so can damage the monitor's circuits and/or the video adapter's circuits.
Some laptops will display on an external monitor without you having to do anything.
If you get no video on an external monitor, some laptops have a key combo that you must press to toggle the display to external video only / sometimes both / built in display video only - see the Owner's or User's manual for the model.
If there is nothing wrong with your AC adapter or it's connection and the jack in the laptop.......
Laptop main batteries usually work as they should for a year or so, then they begin to rapidly deteriorate. From what I've seen, by two years they cannot be charged to anywhere near their full capacity, and it gets worse after that.
They often develop internal shorts when they are older. If the battery gets HOT rather than just warm after you have attempted to charge it for at least a half hour, or after you have been using the laptop for a while with the AC adapter plugged in, it's definitely internally shorted and you must replace it. Internally shorted batteries getting too hot have been known to cause the laptop to catch on fire.
Tips about battery charging problems on Dell laptops - may apply to other makes.
See response 3 in this by iTech: