Get the cheapest SSD you can find that is not SandForce based. You will not get the full power from any SSD as the onboard storage controller is well...low power. Your first concern should be its ITGC abilities. XP means no TRIM...and no TRIM means IDLE TIME is going to be needed to keep it "fast".
TBH I would look at the Vertex PLUS series or the Kingston V series. Both can be found for cheap now. The Indi Martini should be faster than the older JM based controller (toshiba branded) found in the SSDnow V.
NCIX.com - Buy OCZ Vertex Plus 60GB 2.5IN SATA2 Indilinx Arowana Solid State Disk Flash Drive SSD - OCZ Technology - OCZSSD2-1VTXPL60G - in Canada
or
NCIX.com - Buy Kingston SSDNow V100 Series 64GB 2.5IN SSD SATA Solid State Disk Flash Drive - Kingston - SV100S2/64GZ - in Canada
70 bucks is hard to pass up...but YMMV :>