Dual Boot, Dual utrue

I have two hard drives and the classic combination installed on each micro........e XP and UNIX (no not linux), (one OS per drive) and would like to leave it that way. problem is if I want to boot into either I have to go ino the bios and choose the primary boot HD. then reset. is there a way I can get the Unix Loader to recognise the OS on the second HD hence continuing with the standard bototup scenario like as if they were both resident on the same drive?
Thank you those who take their time to reply.

I've never actually ran a pure UNIX machine (only linux and bsd variants). But I do know that linux is very close to unix. I assume there has to be some kind of boot configuration file (like lilo.conf or grub.conf when using those bootloaders). Basically, you'd add a second entry in this file pointing to the main partition of the hard drive with xp on it. That will then transfer control of booting to the windows boot loader when that new option is selected. Or you could go ahead and check and see if either grub or lilo support your version of unix (im assuming they may).

All you need for GRUB

http://geodsoft.com/howto/dualboot/grub.htm#conf

Thanks to the guys who replied I'll try what you said and get back to you.