I have recently bought a new laptop, and as I use Ubuntu on my desktop, but want to play games on my laptop, i installed both windows 7 and Ubuntu 12.04 on the laptop. It all went pretty well, I can boot both without any problems, but i noticed something strange. I divided the 1 TB hard drive into partitions the following way: 10 GBs for the Ubuntu itself, 8 GB for home, 8 GB for swap, and 25 GB for the windows partition. I partitioned the rest as one FAT32 partition-using Ubuntu's disk utility, which said it is around 930 GBs. However, when I boot into windows, it sees it alright, though it sees it as a 875 GBs partition. My concern is not about the space loss, I just don't know what causes the difference, and I don't know if it'll cause any problems in the future.
930 * (10^9) / (2^30) ~= 866. It is possible that Ubuntu disk utility reports 930 GB (gigabytes = 10^9 bytes), while Windows reports GiB (gibibytes = 2^30 bytes). However, this doesn't explain why Windows reports 875 rather than 866.