firstly, you don't need a swap partition... it serves no purpose whatsoever, since the swap drive is the exact same speed as the rest of the drive (a swap scsi disk, maybe, but there's no reason at all to have a swap partition on the same hd unless you're talking about a linux installation).
160 gig is a big hd, but, if you're using windows xp with ntfs formatting, the partitions are merely for organizational clarity... they won't help you with speed or anything else... ntfs reads a 160 gig partition just as fast as a 10 gig partition.
There is some benefit to putting your windows install on it's own partition, just in case it completely crashes and burns, you can reinstall without losing the stuff on your other partitions... but, keep in mind, if things get that bad, it means a complete reinstall and format of the windows partition... which means all the software on the other partitions will have to be reinstalled anyway because their reg/config/inf files are in the windows directory. So, in other words, if you need partitions to better organize things, that's fine... but partitions otherwise using ntfs are not needed at all. If you must partition, there's nothing better than Partition Magic... you can make, remove, resize, reformat, and anything else you can dream of, any partition using that.
Actually, with XP pro, you can use the classic theme, turn off all the transitional animations, turn off shadows and font smoothing, etc... download Tweak UI for XP, and also XP-Antispy, those programs give you almost complete control over all the spying and window-dressing aspects of XP
The thing is, you need anti-virus and firewall protection for any computer connected to the net... and those things do slow down your computer... they're necessary evils... I prefer Norton's AV and Sygate firewall... I believe they're the very best of their kind... but whatever you choose, you need antivirus protection and a firewall.
As for other tweaks... no screensavers (those are a holdover from the 286 days), no power settings... set it so it's always on... it takes more power to turn the monitor back on than it does to just leave it on... but, download xp-antispy, and keep setting things until you have disabled almost everything except things you absolutely need.( http://xp-antispy.org/
I've even gone so far as to turn off all the sound events. And if you're looking for optimum speed, and you don't play games or do graphics, you can set your screen colors to 256... it all depends on how many luxuries you're willing to give up for speed :-)
then again, you have a very nice setup... you're faster than 95% of all computer owners... assuming your computer is clean of spyware, you shouldn't even be worried about speeding things up :-)