Partitioning one physical drive into more than 2 partitions is not all that useful IMHO. As others have mentioned, there is no chance to keep the XP install totally insulated from changes, even in its own partition. Putting the swap file in a dedicated partition on a different physical drive may help a bit in performance though.
Partitioning is useful from an organization POV: different types of data reside in their own partition. I have 3 physical drives (2 partitions on each) and I find it much easier to locate/store data with this arrangement. Also, if Windows gets corrupted for any reason, there is a decent chance that the other partitions will be spared. (Regardless of this, ALWAYS BACKUP, BACKUP, BACKUP!)
@M.Proffit, can you elaborate on the spreading of the PF across different drives? One PF for each drive? Is that not overkill? Any real benefit? Does windows <i>need</i> more than one PF?
@Jimmy greystone, true, there have been many discussions on defrag with arguments for and against. However, the only people who claim that defrag is <i>not required </i> are (no offense meant) random internet posters. Microsoft, and the PC OEMs all recommend defragging regularly to preserve performance. Even in a technet article a few months ago, one of the MS people talked about the need to defrag. On the Vista website, the official guidelines for keeping it running smoothly include defrag. MS even went to the trouble of rewriting the defragmenter from ground up for Vista. I don't think they would have bothered if it was useless. I'd wager that MS knows more about Vista than almost anyone on these forums
So, the choice is whether to believe random internet posters who claim that defrag is not required, or MS (and PC OEMS) who recommend to defrag regularly
Another point: the car revving at redline analogy is totally flawed when refering to disk defragmentation. Defrag is no different from any other disk operation and does not harm otherwise healthy drives.
In certain cases where the files on a drive are static, then defrag may not provide much benefit. For those that see file modification, creation/deletion activity, defrag helps quite a bit in preventing performance loss. What is incorrect is that defrag will suddenly and magically boost performance above the baseline- that is where the confusion comes in, IMO.