You mean you have used up nearly all the hard drive space available. I did follow this hence the question how big is the BootCamp partition. If the MBA came with a small SSD, say 128GB, it is really not big enough. Using Yosemite my iMac with no Itunes nor Movies, and about 50 photographs in iPhoto and only current email messages stored the iMac uses 210MB for EFI, 650MB in the Recovery partition and just on 50GB for the Yosemite operating system.
It could be Windows 7 will use up tp 30GB, after formatting the partition and installing BootCamp drivers etc. That does not leave too much for a small hard drive.