Hi, There is a big difference between a 10 MB file that is laid out contiguously on the disk, and one that is fragmented into a dozen piecesThat's of course true .. that's physics.But .....This "big difference" it's a very small fragment of time .. and will be only noticed by measuring labo apparatus.In the sim it's not measurable at all :)Think at the transfer data rate speed and the speed of the read/write head of a modern hard disk .. and you will understand .. this "big difference" is a infinite small part of time :)I had this experience just for fun (I knowed it was useless)A hard disk fragmented at 37 % (oohh it's huge fragmentation!)I made some time measurements with a 1/20 s chronometer (a mariner chrono)I make the same measurements after defragResults: no visible time difference on the chronoThe myth of better performances for the sim by a defragmentation is one hard to kill :)For my part.. the most bad thing for the sim is if a antivirus (realtime scan) or any programme who check datas is runing.There you have visible difference when the sim run.Cheers.

To the original poster. Historically I have always had a partition for the OS and a partition for apps on a single physical (or RAID array) drive. I was advised to ditch the partition and put the OS on a physical drive (or RAID array) and FS on another physical drive. I have put the OS on a pair of sata II 80gig drives in a RAID 0 (I don`t care about fault tolerance and the read perfomance is nice) and bought one of those new WD 500Gig drives dedicated for FS. I ensured that the RAID pair and the FS drive were attached to different controllers on the mobo. With this configuration I have seen a great reduction in stutters, especially on short final where it really used to annoy me.If you have a big USB hard drive for temporary storage whilst you rebuild your rig I would recommend removing the partition, even if you end up with only one large C drive.Best of luck - I spend as much time mucking around with the pc`s as I do flying! Cheers James