The general approach with such stuff that i recommend is:
1) backup current hard drive image so you can always go back to you current setup (i.e. use a drive imager like Acronis, etc.)
2) backup any of your data files in an easy-to-access way.
3) visit the website of the computer manufacturer and find and download all drivers for your computer (important if you have a laptop since there are commonly special drivers for the network, touchpad, etc.)
4) do a clean install of the new operating system, wiping out the previous one (i.e. never try to do a formal "upgrade")
5) install the drivers
6) do a driver image of the new clean install.
Toshiba is a good laptop maker and their drivers are easily available on the web -- you should have no problem with xp on that machine.