Regarding VM alternatives:
Windows on Intel Macs
There are presently several alternatives for running Windows on Intel Macs.
1. Install the
Apple Boot Camp software. Purchase Windows XP w/Service Pak 2 or Vista. Follow instructions in the Boot Camp documentation on installation of Boot Camp, creating Driver CD, and installing Windows. Boot Camp enables you to boot the computer into OS X or Windows.
2.
Parallels Desktop for Mac and Windows XP, Vista Business, or Vista Ultimate. Parallels is software virtualization that enables running Windows concurrently with OS X.
3.
VM Fusionand Windows XP, Vista Business, or Vista Ultimate. VM Fusion is software virtualization that enables running Windows concurrently with OS X.
4.
CrossOver which enables running many Windows applications without having to install Windows. The Windows applications can run concurrently with OS X.
5.
VirtualBox is a new Open Source freeware virtual machine such as VM Fusion and Parallels that was developed by Solaris. It is not yet fully developed for the Mac - some features are not yet implemented - but it does work otherwise.
6. Last is
Q. Q is a freeware emulator that is compatible with Intel Macs. It is much slower than the virtualization software, Parallels and VM Fusion.
Note that Parallels and VM Fusion can also run other operating systems such as Linux, Unix, OS/2, Solaris, etc. There are performance differences between dual-boot systems and virtualization. The latter tend to be a little slower (not much) and do not provide the video performance of the dual-boot system.
See MacTech.com's
Virtualization Benchmarking for comparisons of Boot Camp, Parallels, and VM Fusion.
Boot Camp is only available with Leopard. The Boot Camp Beta that was used with Tiger has expired and is no longer available for use. So contrary to the other poster's comment, Boot Camp isn't truly "free." You must purchase Leopard to get it.
A single VM can use 1 GB of RAM or more. If you plan to run several of them at the same time, then you will need to consider their RAM needs in determining how much RAM to install.
The Mac Pro can accommodate four SATA drives internally. OS X provides software RAID capability through Disk Utility. Since external drives are slower than internal drives you may want to do Time Machine backups to an internal drive. As for which drives are best, that's dependent on manufacturer, drive size, drive specs, etc. There is no specific answer. But you can find drive reviews and benchmarks at
Bare Feats,
Storage Review, and
Tom's Hardware Review.
For information on adding RAM see the following:
About RAM installation in the Mac Pro
Mac Pro memory arrangement photos
Mac Pro Memory Configuration
Memory Tests- "2008" Mac Pro
Ram should be installed minimally in matched pairs and optimally in matched quads. This means the memory modules are the same size and specifications. They should also be equipped with the Apple-certified style of heat sink.