Acer Support Website: Driver downloads
Bad news neha madan;
Acer has written no WinXP drivers for the Acer 5743z hardware. http://img685.imageshack.us/img685/4716/ss251.jpg
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You won't be able to use WinXP unless you can locate a substitute driver from the manufacturer of each specific hardware item.
For example: Audio Driver, hardware is Realtek. You'll need to search the Realtek site to see if they have an XP driver that will work.
You'll need to do the same thing for each driver you're missing and hope you get lucky.
Seriously, you're better off going with Windows 7.