"I have a 6530"

Latitude 6430 and 6530 series do have XP drivers.

HOWEVER XPMODE in windows has ZERO to do with a particular models drivers.

100 Percent USB Driver compatability is not guaranteed in XP mode.  And XP Mode is not supported by Dell.

http://en.community.dell.com/techcenter/enterprise-client/w/wiki/4373.latitude-6430u-windows-xp-driver-cab.aspx

http://en.community.dell.com/techcenter/enterprise-client/w/wiki/3720.latitude-e6530-xp-driver-cab.aspx

Latitude Systems - CAB Availability (follow the links for CAB details and to download)

System	Windows 8.1 System CAB	Windows 8 System CAB	Windows 7 System CAB	Vista System CAB	XP System CAB
7404	A00 (06/06/2014)		A00 (06/06/2014)
3340	A00 (02/26/2014)		A00 (02/26/2014)
3440	A01 (04/01/2014)	A02 (01/28/2014)	A03 (05/30/2014)
3540	A01 (03/28/2014)	A02 (05/05/2014)	A04 (05/30/2014)
E5440	A02 (03/28/2014)	A02 (05/05/2014)	A03 (05/30/2014)
E5540	A02 (03/28/2014)	A02 (05/05/2014)	A03 (05/30/2014)
E6440	A01 (05/30/2014)	N/A	A04 (05/30/2014)
E6540	A01 (05/30/2014)	N/A	A05 (05/30/2014)
E7240	A01 (03/28/2014)	A04 (05/05/2014)	A04 (05/30/2014)
E7440	A01 (03/28/2014)	A04 (05/05/2014)	A03 (05/30/2014)
3330	A00 (10/23/2013)	A03 (05/05/2014)	A05 (05/30/2014)
10 Tablet	A01 (03/28/2014)	A05 (01/24/2014)
ST2E Tablet	A01 (03/28/2014)	A06 (01/24/2014)
6430U	A01 (03/28/2014)	A03 (01/24/2014)	A08 (05/15/2014)	N/A	A04 (04/30/2014)
E5430	A01 (04/01/2014)	A04 (05/30/2014)	A08 (03/28/2014)	N/A	A06 (04/30/2014)
E5530	A01 (04/01/2014)	A04 (05/30/2014)	A08 (03/28/2014)	N/A	A06 (04/30/2014)
E6230	A01 (03/28/2014)	A04 (06/17/2014)	A07 (03/28/2014)	N/A	A05 (04/30/2014)
E6330	A01 (03/28/2014)	A04 (05/30/2014)	A07 (03/28/2014)	N/A	A05 (04/30/2014)
E6430 E6430 ATG	A01 (03/28/2014)	A05 (05/30/2014)	A09 (03/28/2014)	N/A	A05 (04/30/2014)
E6430S	A01 (03/28/2014)	A07 (05/30/2014)	A07 (03/28/2014)	N/A	A05 (04/30/2014)
E6530	A01 (03/28/2014)	A04 (05/30/2014)	A10 (03/28/2014)	N/A	A05 (04/30/2014)
ST Tablet		N/A	A05 (05/27/2013)	N/A	N/A
2120		N/A	A08 (06/17/2014)	A01 (01/09/2011)	A09 (06/17/2014)
E5420		A03 (05/30/2014)	A10 (11/30/2013)	A00 (03/16/2011)	A09 (05/30/2014)
E5520		A03 (06/17/2014)	A10 (11/30/2013)	A00 (03/16/2011)	A09 (06/17/2014)
E6220		A03 (05/05/2014)	A09 (11/30/2013)	A00 (05/24/2011)	A08 (11/30/2013)
E6320		A03 (05/05/2014)	A12 (05/30/2014)	A00 (03/16/2011)	A07 (05/30/2014)
E6420 E6420ATG		A03 (05/05/2014)	A12 (05/30/2014)	A01 (10/30/2013)	A10 (05/30/2014)
E6420XFR		A01 (09/26/2013)	A00 (05/31/2011)	A00 (05/31/2011)	A00 (05/31/2011)
E6520		A03 (05/05/2014)	A11 (05/30/2014)	A00 (03/16/2011)	A10 (11/30/2013)
XT3		N/A	A09 (05/30/2014)	N/A	A08 (05/30/2014)
13		N/A	A08 (04/29/2013)	N/A	A07 (04/29/2013)
2110		N/A	A04 (04/25/2013)	A00 (12/11/2009)	A04 (04/25/2013)
E4310		N/A	A08 (04/29/2013)	A01 (08/13/2010)	A06 (04/29/2013)
E5410		N/A	A07 (04/29/2013)	A00 (05/13/2010)	A08 (04/29/2013)
E5510		N/A	A06 (04/29/2013)	A00 (05/13/2010)	A06 (04/29/2013)
E6410 E6410ATG		N/A	A11 (04/25/2013)	A03 (08/13/2010)	A14 (10/30/2013)
E6510		N/A	A11 (04/25/2013)	A03 (08/13/2010)	A15 (04/25/2013)
2100		N/A	A00 (12/11/2009)	A00 (12/11/2009)	A00 (12/11/2009)
E4200		N/A	A03 (08/10/2012)	A02 (09/04/2009)	A03 (08/10/2012)
E4300		N/A	A05 (04/26/2013)	A02 (09/04/2009)	A05 (08/10/2012)
E5400		N/A	A04 (06/05/2012)	A02 (09/04/2009)	A05 (06/12/2012)
E5500		N/A	A02 (06/05/2012)	A02 (09/04/2009)	A06 (08/10/2012)
E6400 E6400ATG		N/A	A03 (07/16/2012)	A02 (09/04/2009)	A08 (10/30/2013)
E6500		N/A	A04 (06/05/2012)	A02 (09/04/2009)	A05 (06/05/2012)
XT2		N/A	A00 (11/03/2009)	A02 (09/04/2009)	A02 (09/04/2009)
Z600		N/A	A00 (12/11/2009)	A00 (12/11/2009)	N/A

Thanks for the info on the 6530. I assume if the 6540 gives an error there will probably be no fix for it since no drivers for XP will ever be created. Looks like I will be sending the E6540 and looking for a refurb 6530 or earlier model.

It also gives the same error when trying to go from shared mode on a USB drive to attached. The message is: "Could not attach the USB Device. You can attach USB device to a different USB port or restart the virtual Machine and try again". Tried both restarting and switching USB ports with no luck. My 6530 does not have this issue. :(