partitioning - How can I shrink my Windows partition further than the disk management is allowing?

I just bought a new computer with a 2TB hard drive that has only a single partition. I would like to divide this into at least 4 partitions, but when I try to shrink the current partition, it says the total size is 1888171 MB and that the size of available shrink space is only 939075 MB. The used disk space is at 40gb right now - why can't shrink it to somewhere around that?

I read here: http://www.howtogeek.com/howto/windows-vista/working-around-windows-vistas-shrink-volume-inadequacy-problems/ that this is because of unmovable system files. I doubt this is the only problem though.

I would like to get this partition down to 500GB. How can I do this?

edit: So I've learned that 4 partitions is the max allowed on MBR. I realize this makes it sound silly that I said I wanted "at least 4". Time to learn how to use GPT :/

Answer

GParted should be able to change the size of the partitions as you want, it can be downloaded from GParted Live CD

BTW, you can have only 4 primary partitions, but if you create one extended partition you can have more logical partitions.