You might want to consider making sony recovery disks.
I have no idea how to do that with a Vaio.
After you make those, then you will at least be able to get back to the original state of the machine if all goes wrong.
Check to make sure that your computer is capable of running Win 7.
First you want to download and run the Upgrade Advisor. Upgrading from Windows XP to Windows 7 - Help & How-to - Microsoft Windows
Here is a link with video on what you want to do, namely upgrade from XP to Win 7:Upgrading from Windows XP to Windows 7 - Help & How-to - Microsoft Windows
Another approach which I've used on a Vaio, but not with Win 7, is given here: SSD / HDD : Optimize for Windows Reinstallation
After following this approach, then you can go the Sony site and get any driver updates specific to your computer. I definitely would not install the Sony bloatware.