Open the I386 folder on your XP CD and find a file called SETUPP.INI. That file will contain a line starting PID=
The numbers following the ‘=’ indicate which version of XP is on the disc.

Here’s a list of all the various types of disc along with the volume name, date and PID numbers:
Windows XP Home Retail = WXHFPP_EN 08/23/01 8:00 AM (08:00:00) 55277000
Windows XP Home Retail w/ SP1 = XRMHFPP_EN 08/29/02 8:00 AM (08:00:00) 55277000
Windows XP Home Retail w/ SP1a = X1AHFPP_EN 03/31/03 8:00 AM (08:00:00) 55277000
Windows XP Home Retail w/ SP2 = VRMHFPP_EN 08/04/04 8:00 AM (08:00:00) 55277000
Windows XP Home Upgrade = WXHCCP_EN 08/23/01 8:00 AM (08:00:00) 55285000
Windows XP Home Upgrade W/SP1 = XRMHCCP_EN 08/29/02 8:00 AM (08:00:00) 55285000
Windows XP Home Upgrade W/SP1a = X1AHCCP_EN 03/31/03 8:00 AM (08:00:00) 55285000
Windows XP Home Upgrade W/SP2 = VRMHCCP_EN 08/04/04 8:00 AM (08:00:00) 55285000
Windows XP Home OEM = WXHOEM_EN 08/23/01 8:00 AM (08:00:00) 55277OEM
Windows XP Home OEM w/ SP1 = XRMHOEM_EN 08/29/02 8:00 AM (08:00:00) 55277OEM
Windows XP Home OEM w/ SP1a = X1AHOEM_EN 03/31/03 8:00 AM (08:00:00) 55277OEM
Windows XP Home OEM w/ SP2 = VRMHOEM_EN 08/04/04 8:00 AM (08:00:00) 55277OEM
Windows XP Home Volume = WXHVOL_EN 08/23/01 8:00 AM (08:00:00) 55274270
Windows XP Home Volume W/ SP1 = XRMHVOL_EN 08/29/02 8:00 AM (08:00:00) 55274270
Windows XP Home Volume W/ SP1a = X1AHVOL_EN 03/31/03 8:00 AM (08:00:00) 55274270
Windows XP Home Volume W/ SP2 = VRMHVOL_EN 08/04/04 8:00 AM (08:00:00) 55274270

Windows XP Pro Retail = WXPFPP_EN 08/23/01 8:00 AM (08:00:00) 55274000
Windows XP Pro Retail w/ SP1 = XRMPFPP_EN 08/29/02 8:00 AM (08:00:00) 55274000
Windows XP Pro Retail w/ SP1a = X1APFPP_EN 03/31/03 8:00 AM (08:00:00) 55274000
Windows XP Pro Retail w/ SP2 = VRMPFPP_EN 08/04/04 8:00 AM (08:00:00) 55274000
Windows XP Pro Upgrade = WXPCCP_EN 08/23/01 8:00 AM (08:00:00) 55276000
Windows XP Pro Upgrade w/ SP1 = XRMPCCP_EN 08/29/02 8:00 AM (08:00:00) 55276000
Windows XP Pro Upgrade w/ SP1a = X1APCCP_EN 03/31/03 8:00 AM (08:00:00) 55276000
Windows XP Pro Upgrade w/ SP2 = VRMPCCP_EN 08/04/04 8:00 AM (08:00:00) 55276000
Windows XP Pro OEM = WXPOEM_EN 08/23/01 8:00 AM (08:00:00) 55274OEM
Windows XP Pro OEM w/ SP1 = XRMPOEM_EN 08/29/02 8:00 AM (08:00:00) 55274OEM
Windows XP Pro OEM w/ SP1a = X1APOEM_EN 03/31/03 8:00 AM (08:00:00) 55274OEM
Windows XP Pro OEM w/ SP2 = VRMPOEM_EN 08/04/04 8:00 AM (08:00:00) 55274OEM
Windows XP Pro Volume = WXPVOL_EN 08/23/01 8:00 AM (08:00:00) 55274270
Windows XP Pro Volume w/ SP1 = XRMPVOL_EN 08/29/02 8:00 AM (08:00:00) 55274270
Windows XP Pro Volume w/ SP1a = X1APVOL_EN 03/31/03 8:00 AM (08:00:00) 55274270
Windows XP Pro Volume w/ SP2 = VRMPVOL_EN 08/04/04 8:00 AM (08:00:00) 55274270
Windows XP Pro Tablet PC w/SP1 Disc1 = XRMPFPP_EN 08/29/02 8:00 AM (08:00:00) 55274000
Windows XP Pro Tablet PC w/SP1a Disc1 = X1APFPP_EN 03/31/03 8:00 AM (08:00:00) 55274000
Windows XP Pro Tablet PC w/SP2 Disc1 = VRMPFPP_EN 08/04/04 8:00 AM (08:00:00) 55274000
Windows XP Pro MSDN = WXPFPP_EN 08/23/01 8:00 AM (08:00:00) 55274000
Windows XP Pro MSDN w/ SP1 = XRMPFPP_EN 08/29/02 8:00 AM (08:00:00) 55274000
Windows XP Pro MSDN w/ SP1a = X1APFPP_EN 03/31/03 8:00 AM (08:00:00) 55274000
Windows XP Pro MSDN w/ SP2 = VRMPFPP_EN 08/04/04 8:00 AM (08:00:00) 55274000
Windows XP Pro Evaluation = WXPEVL_EN