Before you even think about upgrading WinME to WinXP you need to check your computer spec. Processor speed, memory, hard drive size. Now for gods sake don't use M$ minium spec as they only wanted to sell WinXP when it first came out Windows XP Professional System Requirements
128MB RAM yes if you want to make a cup of coffee and drink it before something loads. I think 500MB is ok and memory is quite cheap.
233MHz processor again you can make another cup of coffee. 500MHz plus would be better.
1.5GB hard disk space, ok thats just for the system to install and operate not for saving any large files. I've had WinXP on my old computer with a 20GB hard drive with plenty of space for other things.
If your converting from a WinME system check the graphics card, sound card, printer and scanner etc if WinXP drivers are available else thats more bits of hardware you're going to need.
Windows ME (spare computer)
Windows XP 2002 Professional SP3 (desktop computer)
Windows 7 Professional SP1 32bit (laptop computer)
Windows 8 64bit spare drive for laptop computer