there is a Windows XP Paper Licence available(to run all systems with one single serial key),
oopps... i dont think there any such thing can be done... what i know from my experiance is Volume license is there for u... totaly diffrent from what u r thinking... we have our cafe... which runs on Volume lisencing...
Basically what happens is we get ONE installation pack only which holds a pre activated XP copy... and all other systems get only one CD Key...
like 1 CD/DVD pack (useally it contains many more stuff) for 50 system but all system has their own CD Key... u have to buy all those CD key...
benefit is u can istall as many time u want in as many system u want, OEM wont allow u to uninstalll from system A and then install the same copy in system B but some form of volume Licence will allow u to do such, just keeping in mind that u run as many system as u have Licence to...
also u may copy the CD to keep more copies at ur hand...
i see u r from Kolkata... we have MS office at Camac Street just beside the BCL... u may contact there for further details... as there huge discount available when u getting many license...
or u may ask MS to come to u... if u r buying many Licence MS exicutive will contact u at ur place... ohh another thing is... here with many Licence... u can do a little Bargaining....
lol....
anyway here is the links what matters to ur need...
Volume Licence Home Page
Microsoft India Contact Page
hope this helps....