Hi Ravi, there are many certain condition in which people will think to go back to WinXP... Many many businesses run custom build applications for their setup and many time due to lack of support from the software developer, that cant be implemented in an upgraded OS..
I am just giving you an example, in our case our cafes have license for vista with farely higher end systems (X2 / DC / C2D + 1GB+ RAMs) but we are forced to use XP as the cafe management software didnt give us free upgrade to Vista compatible versions (CafeZee)
hence unless we buy a new vista supported version of that application, we cant switch to vista !!!