Windows 7: Windows XP Pro won't recognize external drive formatted in Windows 7

I did try to find this topic with a few searches; I hope this hasn't already been covered.

I bought an external bare SATA II drive docking station (BlacX Duet) and a WD Caviar 2 TB drive to go in it. I'm using the USB cable interface to attach it to my Windows 7 Pro laptop (MacBook Pro on Bootcamp).

Drivers installed automatically, etc., no problems. I created a single primary partition on the drive and formatted it NTFS. No problems/issues in Win 7 using the drive.

My intent is to use this for backups on multiple computers.

Well, I attached the unit to my Dell Inspiron 1525 laptop running Windows XP Pro, drivers installed automatically. It recognizes the presence of the drive in Disk Manager, but it does not recognize the NTFS partition that I created in Win 7 on the other laptop.

What am I missing here, or what did I do wrong?

There is an older similar thread here, but no solution:

XP cannot access other drive with Windows 7 dual boot

After further investigation, I noticed that the drive appeared in the disk management utility on Windows XP as a "GPT protective partition", thus Win XP could not access it.

This came about via my own lack of knowledge when I initialized the new disk in Windows 7 and selected "GUID partition table (GPT) partition style". I should have selected the master boot record (MBR) method.

I couldn't figure out how to revert the disk. A quick web search for "GPT protective partition" led me to this page:

How to delete GPT Protective Partition - Paul Gu|blog

In Win XP, I followed the command prompt instructions given on that page, and re-initialized, formatted NTFS, etc. Now the drive works fine in both OS

Fortunately I had very little data to lose, but it was an exercise in wasted time due to my own ignorance.

Thanks to AddRam for some good advice as well (Partition Wizard Bootable CD) - Had I heard it before I reformatted it may have saved me some time and effort