Upgaded to Win7 - do i have to keep my XP system/disks

I seem to have upgraded sucessfully - a clean install over my 32 bit XP SP3 using Windows & Professional x64 Upgrade disk. I back up the system regularly using macrium reflect, so i should be OK in the case of a serious problem. However, if i had to do a clean install after some unforseen catastrophe, how would i go about it? I mean would i do better to keep my old XP on its old SSD (i...