Q: After defrag, why does "other" storage increase on my HD?

Background: MacBook Pro (mid-2010), currently running Lion.

I needed to partition my hard drive to run Windows 7 for a class that I'm taking at my university. I read online that defragmenting the Mac hard drive would allow the user to easily install Windows, so I downloaded the application called, "Disk Genius" to defrag my HD. After the defrag I noticed that my USED storage space had increased from 65% to 83% and I saw that the "other" category was occupying all of the newly used space. Now I don't have enough space to efficiently run Windows 7. I have deleted so many old files from previous semesters and emails, ect., but the space is still there.

Anyone have any ideas?

I have tried using Time Machine, but it doesn't take me back to previous dates.