What do you mean the Windows 7 you have is on more than 3 pc's. Are you trying to Clean Reinstall - Factory OEM Windows 7
which came preinstalled on the Dell? If so use the Product Key on the COA sticker to reinstall only the licensed version. If not then how do you plan to activate it?
Download Hiren’s BootCD 15.1
to write to flash stick Hiren's BootCD From USB Flash Drive (Pen Drive) »
boot into Partition Wizard from Hiren's boot menu to Quick Wipe the HD, then partition it NTFS Primary, rightclick to Modify>Set to Active. This may be enough to get the booted Windows 7 installer to detect the HD and install.
If not you can boot into XP on Hirens to install the BIOS update.