Can you confirm you didn't select the 64-bit versions of XP while creating the VM? Anyway, in order to support newer and 64-bit guests, boot you host into the BIOS and enable "VT-x" as well as "No Execute Disable/NX". Then - after saving the settings - power cycle the host system (a simple reboot might not be sufficient). If this still dosn't help, attach the VM's vmware.log file located in the VM's folder to a reply post (use the Advanced Editor).
André