The problem is one of definition. If you were to use XP's System Restore, you need to define how much space to let it have based not only on the OS installed on the bootdrive, but add-ons that may be installed there.
Load up XP with IIS, Visual Studio, and more busts past the 10GB point in no time.
Your question can't be answered with what's in your post.
WinXp home 512 MB Ram 2.4 GBP4 160GB Seagate HD
What is the minimum primary partition size for operating "normally". I know 4Gb is too small for me now.