I hate to side up to Microsoft's messages here but on a selfish point, it's no longer what it's cracked up to be. While Windows XP has been given another reprieve until 2015, Windows 7 SP1 has been recently released giving those in the enterprise the reliability and security they didn't feel they could get from the initial release.
But these arguments are superficial frankly. I doubt you could find one person to give a single, good reason to convince every single XP user to upgrade to a newer alternative. If such a golden key answer was indeed possible, surely every operating system manufacturer would have used it long ago.
This coming semester when, or if, you buy yourself a new laptop - you'll be saddled with Windows 7 no doubt. Unless you're going for a netbook, then keep with the times and make the leap. Even then, there's no reason not to jump aboard the Linux train.