My XP DAW still boots in under 45 seconds. That's complete - no hourglass or flashing drive light. Ready to go.
Its about 4 years old. The key, as Matt said, is to not load stuff on it that starts running processes when the system starts. Using prudent install rules you can keep it this way and not slow it down.
Don't put anything internet on it (no browser or antivirus)
If you install any graphics or camera stuff go through the processes so they don't load anything at startup; only when needed (manual start in the computer management - services list)
Hopefully you have a nice big clean partition for the Temp Audio Stream in the audio preferences area that is separate from the main drive XP runs on..
Keep your RB/Backup or PT/Backup folder clean before defragging every so often.

These tips have served me well for stability and quick startup over the last few years.
One of my instructors tells me I can shorten the start up time more by using a few registry edits that keep the windows prefetch list small, etc. I'm happy the way it is; "if it ain't broke don't fix it"

I do not work here, but the benefits are still awesome
Make your sound your own!