One would assume that below a certain amount of storage space left, the performance of a hard drive decreases in WRITE speed as it requires more time to find blocks to write to since there are less consecutive blocks. I think I ran into FRAPS performance "lag" due to this problem once I dipped below 10GB of free space on my HD. Once I had cleared up some old FRAPS footage and had 60gb+ I had no "lag" at all. I would research my theory, but I have no time :o To add: HD performance issues occur when there is high fragmentation. This is because data is stored in the HD in blocks, and the read/write head of the hard drive has to find these blocks to read/write to them. If these blocks are in a consecutive order, the data can be read quickly. However if the data blocks are fragmented, the read/write head has to locate each block to read and assemble the file. Files become fragmented when free space on the HD is not large enough to contain the whole file and so the file is split into multiple sections which are then written to other free areas of the HD. fyi, huge guess