My PC has a roughly similar spec to yours, and runs XP Home. Boot-up (including startup of wireless network and broadband connection) is around 1 min 30 secs.
Has this slowdown happened gradually over a long period, or suddenly/recently? If the latter, you could try using System Restore to roll back to a date before the problem started.
Things that can substantially extend your boot-up time are:
1. Having a lot of unnecessary stuff in your startup folder.
2. Some antivirus software, particularly if it scans a heavily laden startup folder every time you boot up.
Try using a utility such as Ccleaner to give your computer a good spring clean. click here