I just got my m1530 a couple of weeks ago and the first thing i did was reformat it down to XP.  My OEM copy of XP Pro SP2 didn't want to install on my notebook, it couldn't detect the hard drive, but I had a spare Dell XP disc that came with another machine and it worked without a hitch.  The toughest part was finding drivers since all of the support for the XPS laptops through Dell are all for Vista.  One thing I did was download the Network card drivers from the Inspiron series, since they have XP drivers listed on the site, which worked perfectly fine, then did a Windows update to find as many of the hardware drivers for me as possible.  And the rest i just did a google search for the drivers.

Good luck! 

Really easy to downgrade:

1. Get into the BIOS and disable the Intel Flash Cache Module, and change the SATA Operation from AHCI to ATA.

2. Format your HDD using the Dell Media Direct disk.

3. Install Win XP.

4. Install Media Direct.

5. Install all the drivers that are on support.dell.com for your computer, remember, the order for them is: Notebook System Software, Chipset, Ricoh, Video, Audio, NIC, Wireless, BT, Laptop Camera, Fingerprint, etc. If you are looking also for QuickSet you will have to search for it on the top, search for a XP verison.