I have a triple boot setup that works smoothly, I did a fresh wipe about 8 months ago accompanying a hardware mostly hard drive up grade. I now have all my data and ISO's on my "older" 320gb harddrive.
I have dedicated my newer drive to operating systems initially installing Vista64 bit onto primary boot partition leaving 4 extra spare partitions.
since then I have installed win7 beta a few times until that partition now has win7 RC1 running happily. I have also setup one partition as "shared installs" and winxp for my studying for my MCDST etc
Used EasyBCD to manage the boots
I have occasional permission problems with the data partition mutually shared between all 3 OS, and with sharing installs the limiting factor seems to be where reg keys are essential, In this case the program needs to exist exclusively on each OS mainly for recognition as default programs
Well, my system:
1, Maxtor 160Gb, for Page Files, User Data, Installed Programs for all 4 OS's. Single program installations w/shortcuts pinned to each OS Taskbar
1, Maxtor 160Gb, Windows Vista SP2 x86
1, Seagate 250Gb, Windows Vista x64
1, Seagate 320Gb, Windows 7 x86
1, Seagate 320Gb, Windows 7 x64
And I run Windows Xp in VMWare
And everything is running great
Removed the 160Gb, IDE moved everything off that drive and placed it on a Maxtor 250 SATA, put in another Seagate 250 SATA to run XP, re-installed Vistax86/x64 on 1 Seagate 320 SATA and re-installed Win 7x86/x64 on the other Seagate 320 SATA.