I am presently booting Win 98, Win XP, Linux - Knoppix, Mepis & Xandros on one machine and the same with a second but with Fedora C4 in place of Knoppix. This is without problems using the windows Boot.ini file. All these OS/Distros are blissfully unaware of each other and there is no cross interference.
This took quite a while to achieve with the inevitable stuff up. However, once this was done and the dust settled it was quite easy. Actually there is no limit (within reason) to the number if Linux/Windows OS you can boot into.
I have detailed the procedure in a 2 page PDF file and included 2 free small programs (MBRWIZ & BOOTPART).
The link to the multi_system_boot.rar file is shown in my 4th post below.