how do i set up a dual os boot so i can use winxp programs?

i haven't been able to set up a dual partition boot for ubuntu 10.10 and winxp. i've got more than enough memory , a 500gb harddrive, and a penti 4 driving it all... and when i install either , they block the other from booting, or the option from appearing on start-up. i'm new to linux, but not a fool. i just lack information. i suppose i need a book, too, but i was hoping someone could drop me a clue on where to look in the system, or give me an example or instructions to work from....

thanks for any help!