Have both the A205 and A305 Toshibia loptops
The A205 I Downgraded from Vista to XP - Not Problems. Later I upgraded to Win 7 RC - again no problems. However I now have to decide if I want to (1) go back to vista (still have HDD0, (2) reconnect HDD w/XP, or (3) upgrade to Win 7. Will probably go with XP or win 7 Vista is a resorce hog for lower end Laptops, Win 7 is better, but don't know if it's worth the $100. Upgraded A305 to Win 7 and a Blu-ray Player/dvd writer and memory to 4 gigs - Stayed with 32 Bit.
I see Toshibia list a modem drivers for the A215-S5822.
For XP SP2/3 it's Ver 2.1.01 dtd 09/18/2007 (For XP/XPSP2&3/Vistahttp://www.csd.toshiba.com/cgi-bin/tais/support/jsp/modelContent.jsp?ct=DL&os=&category=&moid=1909315&rpn=PSAFGU&modelFilter=A215-S5822&selCategory=3&selFamily=1073768663
I would assume that you installed XP and have it with service pack 3
Have you upgrated XP to SP3 and did you load all the drivers from the list.
After that goto XP update and scan for updates, look at optional for Hardware.