I have my basic software set installed on Vista. (The software that I use
the most frequently) and I'm using 15GB. If you're using less than 15-20GB
currently for XP, you'll probably be okay to make two 30GB partitions. If
you're using more than that, it might get risky. If you're using less than
10GB on XP, go ahead and make a 20GB partition for XP and a 40GB partition
for Vista. Another important note though is to backup all your data before
making partitions because unless you use special 3rd party partitioning
software, all data on the hard drive will be erased. Even if you use 3rd
party software that will not erase your data, you'll still be better off by
backing up your files. I would recommend disabling system restore on
computers with smaller hard drives because system restore will eat a lot of
hard disk space on Vista - more so than XP. You should be able to bring
your partitions back together later, but once again, you'll lose your data
on both partitions.
Here's what I have installed on Vista:
Sierra PrintArtist 8.0
Adobe Photoshop 5.5
Nero 5.5
Avast! AntiVirus 4.7
Ares 1.9
ATI Catalyst Control Center
Audacity
Creative Drivers
DAZ Bryce 5.5
DEX Phone Book
Gaim
HP PhotoSmart Photo Printing Software (I like the software but not their
printer. I'm using a Canon i560)
iTunes
Lavasoft Adaware SE Personal 1.06
Microsoft Office 2007 Professional Plus
Microsoft Plus! for Windows XP (Most of it works on Vista)
Mozilla Firefox 2 Beta 1
MumboJumbo games - Super Collapse, Super Glinx, and Super Nisqually
Paint.NET
Quake III Arena
QuickTime
Rio Music Manager