Not Enough Space on Disk message

I was able to make an unallocated partition of 5.27 G on my drive, but when I attempted to use the Simple Volume Wizard to convert it to my XP NTFS partition, it gave me the message "Not enough space on disk". Admittedly, the initial screen with G ranges showed more space than the partition graphics did, but I reduced the maximum part of the range to a lower figure with no effect. Any ideas?
Phil