The reason for no F8 menu is because you overwrote the WinRe file in Win7 which provides the System Recovery Options
which is where the Dell Recovery hotkey was rooted.
Without the Dell Recovery disks your options now are to Clean Reinstall Windows 7 Factory OEM
or to order the Recovery Disks from Dell. However on many models they only provide a Win7 REinstallation DVD so you might as well use the DVD in the blue link and get the same clean reinstall now - if you didn't make Recovery Disks.
Once you reinstall Win7 you might be able to recreate the link to Dell Recovery Partition - restoring F8 link
. So for that reason you might want to save Recovery Partition as well as the Dell Tools partition if it will run from its hotkey which is normally separate from F8.