^+1 Agree. Delete all the partitions, and install.
Yes, you will loose any changes to recover any "Dell" files, as you are overwritting Dell's Vista with Windows 7. It's ok. Dell has alot of "garbage" on there OS's.
Windows 7 will create a partition, 100MB, called "System Reserved." for important OS files, LEAVE IT ALONE!
NOTE: You will loose any of your important files (i.e. Music) when you repartition and format. SO BACK UP FIRST!