is there any way...
 

That once i have linux installed that i can install WinXP?

i know that you can easily install linux, with XP installed already. but can you do it visa versa?

You can, but be warned: XP will likely overwrite your MBR. So be prepared to reinstall LILO or GRUB. A search of L will bring up a number of threads on how you do this.

Also probably best to resize your partitions first before the XP cd gets anywhere near your machine.
And backup your stuff.