Not advisable if you do not have a Windows 7 disc to return it back to orginal, if things don't work out.
Down grading to an older Windows version is time consuming.
1. Make sure the computer manufacturer has XP drivers for your computer. They may even have a Windows XP version of software for your computer.
2. Download then and burn then to a data CD
3. If they have no XP drivers you need to print out what hardware your computer has. You use this to go to their Web sites to get the drivers.
4. Once you have all of this, you can begin
5. Boot the Windows XP CD and have it delete the current partition.
6. Now have it partition to NTSF, when it finishes it will install the Windows XP operating system.
Word of caution, be aware that you may not be able to get exactly the drivers you need, there may be an alternative for those. Like I have said it is time consuming. Wish you the best of luck. Be also aware the a Toshiba may be the hardest one to down grade.