If you tried to install NEW Cannon printer with drivers for Windows 8, on a 'old HP Pavillion 7480 desktop' that has XP / Vista, you then hosed up Windows and you would need a Windows Disk to do a repair. Doesn't matter if your a struggling artist, you will still need to spend money to do repairs on things.
Depending how old this computer is, you may just find it is cheaper to get a new PC. If this is a old XP system,
1) you can't call for support as that computer is LONG AGO on the no longer supports list
2) you can call to BUY a replacement copy of Windows as XP/Vista/7 are no longer 'issued' or carried by the makers.
So this leave you with going to Walmart/Bestbuy/whereever and buying a new copy of Windows8.1 Update, which is $179+ . For only $249 you can get a simple laptop or desktop PC at same stores, all UNDER WARRANTY, with a new copy of Windows8.1 Update, and performance probably alot better then you been 'used to' with that old system.