The recovery partition that is present in the Dell notebook is created by Dell not Microsoft Windows that is there in case if you want to roll back to factory settings without having the installation media(usually there is a key combination that one has to press to go to the recovery environment where the Recovery manager provided by the OEM in this case by Dell will handle the further recovery options) If you are installing Windows 7 on a brand new notebook don't worry about the recovery partition just partition the drive as follow:
I would recommend nearly 50 Gb for the C drive(i.e. the partition where you will install the windows 7 and other application softwares)
Partition the rest as per your need or you can keep the remaining as one usually people partition the disk for different works like Study,Entertainment etc. anyway it's a personal choice.
In case you need to recover or reinstall windows you can do that by formatting the C partition without even touching your data.
So,go ahead and install windows 7 and do keep the installation media safe it would help you in future to reinstall or to boot into recovery environment.