You can partition the drive and install XP (complicated, unless you have experience with partitioning).
Easy option for running XP inside Win8 would be to use a Virtual Machine. You can use
Virtual PC (from MS) or
VirtualBox (Oracle). Both are free. Most modern CPUs support visualization, so you can get pretty good performance even with low end PC.
Better yet, just get use to Win8 UI. Once you are accustomed you will forget XP. Start hitting that Windows Key