Installing Vista (Partition Space?)

Hey everyone.

I'm trying to install Vista over XP. It's giving me an error telling me that I need "at least 405 MB of space on the F drive."

My partitions:

C: 35 GB of 145 GB
D: 3.39 GB of 3.39 GB
F: 26.4 MB of 39.1 MB

E is the disc drive.

When I reformatted a couple of years ago perhaps I did something wrong with the partitions. I don't need to reformat, do I? Your helpful input would be appreciated.

My Specs:

Computer: Dell XPS 400
Processor: D
Memory: 4 GB
OS: XP