Partitioned drive, 2 OS's, how do I switch?

People seem to know what they're talking about around here so I'm asking here before starting my own research with google.

XP on one partition and Vista on the other. I was able to switch back from Vista to XP by going into System Properties - Advanced tab - Startup and Recovery. Under those same conditions in XP however, I do not have the option to select Vista as my main bootable OS. I made a post earlier about Acronis OS Selector and how I was having issues with it, so that's out of the question. Does anyone know of a simple way to switch between these 2 OS's from within XP or possibly another 3rd party software? Thanks in advance.

you can just use the windows bootloader to swap the OS when you start the computer

type in C:\boot.ini to the run command box from windows xp and make sure theres these 3 lines somewhere in the file:

timeout=30

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="XP" /noexecute=optin /fastdetect

multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Vista" /noexecute=optin /fastdetect

if you have more than 2 partitons youll have to change the partition values and if theres more than one harddrive youll have to change the rdisk values

but... that should have happened as default anyway when you installed vista so im not sure what went wrong