Hey arti, I don't know if you ever got this problem resolved, but i was living with having to power off my PC by hitting the power switch on my power supply for a few weeks after upgrading to XP. Windows shut down as it should but the PC wouldn't power off, although it used to with 98 2nd edit. I found a topic called "computer does not shut down" in the 'computer hardware' forum that had a link to a site where I found a solution. Link is
http://aumha.org/win5/a/shtdwnxp.htm Look under "Powerdown Issues" on that page. There I found the solution that worked for me. I quote it below:
"When Windows XP won’t powerdown automatically, the APM/NT Legacy Power Node may not be enabled. To enable this, right-click on the My Computer icon, click Properties | Hardware | Device Manager | View. Check the box labeled “Show Hidden Devices.” If it’s available on your computer, there will be a red
X on the APM/NT Legacy Node. Try enabling it and see if this resolves the powerdown problem (Tip from Terri Stratton). Or, to check the other side of the APM/ACPI coin, open the Power Options applet in Control Panel. If there is an APM tab, make sure the “Enable Advanced Power Management Support” box is checked. (MSKB 313290)"
Maybe this will help.