Trimming boot speeds can be a bit of a fiddly art, and bit of luck.
Removing/disabling as much hardware as possible speeds up things, as the OS initialises everything it detects. Most Motherboards these days are very integrated - Audio/Lan/Floppy/Ide/Raid/USB/Parallel/2xSerial/Ps2 is standard. If you don't use it - disable it in the bios (e.g. Floppy/1xide/raid/serial/paralllel/ps2 are often unused). This prevents the OS loading the driver and waiting for it to initialise the hardware. Having said that, XP performs this task much faster than previous windows.
Also disable the killer services - like Indexing, system restore, windows themes, any anti-virus, networking stuff (unless you need it!). Set you windows paging file to one size only (ie same min and max) so it doesn't waste time resizing it.
Once you're happy you've slimmed it all down, run a defrag - boot up is massively harddisk dependant. Using a fast hardisk as your boot drive makes the world of difference - a 8meg cache 7200rpm Hitachi or 10k WD raptor affair, while more pricey, boot noticeable faster than a generic 160 gig drive. They tend to have firmware optimised for desktop use as well, so these drives can even outperform high-end scsi drives on bootup times as scsi tend to be optimised for workstation applications.
And finally - keep booting. XP auto-optimises bootup and application starts after set intervals (read up on BootVis on the MS website) so you should find things improve (slightly) over time anyway.
Of course, there is always PLAN B: ;-)
Buy a "HyperOs HyperDrive III" from
http://www.hyperos2002.com/These badboys are basically ram harddrives - apparantly you can install XP from scratch in under 5 mins on them. They are also silent. You could buy a 2gig version and use it as a boot drive.