[BF-109 F4]

This is one of the most strange problems i ever had in my PC and i have no idea how to solve it. A low disk space warning just popped out and when i went to see my free space my 1GB that was left is gone. had only 152 MB and could sit there and watch the space decreasing even more to 0 bytes. when reaches 0 i can't open the Internet or any softwares and my PC doesn't get slow as predicted.
Any ideas? :???: