Win 7 is better than XP under one condition: When the CPU has 4 or more cores.
If what you have is a 2-core CPU, stick with XP.
If what you have is an older generation of 4-core CPU, stick with XP.
If your CPU is i7 or better, go for Win 7.
But before you go for Win 7, my advice would be check out newer releases of Linux distros such as Ubuntu.