I want to upgrade my desk top pc from xp home premium to windows 7.?

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You cannot upgrade directly from XP to Windows7

You CAN upgrade from XP to Vista

And you can also upgrade from Vista to Windows7

I know of no one who has done BOTH steps, and very few computers have hardware
that is compatible with all three operating systems (Typically only a handful of HP and
Dell Buisiness computers)

And generally speaking only computers with an Intel Chipset 925 or newer.

Your Dell 3000 uses the Intel 865 chipset.
From experience even the intel 915 chipset doesn't finish loading windows7 before the installer crashes