I just thought I'd draw attention to an unsupported Microsoft tool that can help decrease boot time in Windows XP. It's called BootVis and is not available for download from the Microsoft web site (and hasn't been for quite some time).
The reason the tool is not available for download is, according to Microsoft, that the actions performed by the utility are automatically performed by Windows XP every three days. Meaning it shouldn't really have any effect.
But if XP does this automatically, why do I see such a dramatic improvement on all the systems I've tried it on? I remember using the tool a few years ago on my home workstation and was really surprised at the effect. I cut down my boot time by about 70% (I don't remember the exact numbers).
So after installing XP back on my laptop, I downloaded Bootvis again and ran it. Now, instead of booting to useable state (meaning, to my desktop) in ~70 seconds, I'm there in under a minute now.
So, how do you use bootvis? Well... first of all, download it from here, thanks to the guys at Major Geeks.
When you run it, you want to hit the Trace menu and select Next Boot + Driver Delays. Now allow the program to reboot your machine. If you need to log in when it's back up, do so but don't touch anything else until Bootvis is back up. Now it has finished profiling your system and is ready to optimise it. This is also done on the Trace menu - select "Optimize System". Your machine will now begin the optimisation process and then reboot. Once again, allow bootvis to load completely before touching anything. When it's done, try a last reboot and see if you can feel the difference.