Probably this is yet another noob question, but, i'm not understanding why this happens..

I had a BT4 R1 USB Persistent stick, but i was having performance issues, so, i've installed BT4 in dual-boot in my HDD, in a 7GB partition.. I choose 7GB of space cuz in my stick i had even more software and files that i have in my HDD partition, and the volume never exceeded 4GB (8GB stick btw)..

The performance issues are gone, but now, after a fresh installation, BT4 occupies 6.5GB instead of the usual 2.. And i really can't understand why the installation space tripled.. Now i'm having low disk space errors all the time, with only 220Mb of free disk space..

My question is, is there a way to solve this without changing the partition size? And why does the volume gets >3x bigger that in a USB Persistent?

Thanx in advance.