What are you intending to upgrade?
If it includes a new motherboard then it would be wise to do a Repair (NOT install) of XP as it doesn't always like the change of circumstances with a new mobo. You will also preserve your configuration and data.
Don't forget to configure the Bios to boot from CD-ROM (i.e. your XP CD-ROM) before doing the Repair. There are several threads on the subject or go to:
You will also need/may need to reinstall SP2 and any subsequent SP3 updates if you don't have a slipstreamed XP-SP2 disk.
As for the normal type of upgrading XP should take it in its stride when you commence installing new components etc, although getting the very latest drivers will be of value once it is up and running.