I think I've got the MDRIVE.SYS question solved: the CONFIG.SYS line takes a parameter that sets the multiples of 64 Kbytes allocated to the memory drive. The line device = mdrive.sys 2 will allocate 128 Kbytes to the memory drive (some of which is used for the boot sector and FAT). The limit appears to be 704 Kbytes, set by parameter=11. Any higher number just gets adjusted downwards to the maximum 704 Kb. Directory entries are allocated in units of 48, and I've not been able to find a parameter to adjust that (as some RAMDRIVE drivers can). Also, sector size is always 512 bytes; a figure of 128 bytes would be desirable, but again, I cannot find a parameter to set sector size either. If you enter the CONFIG.SYS lines device = mdrive.sys 3 device = mdrive.sys 3 this will cause *two* memory drives to be set up with 192 Kbytes apiece, with consecutive drive letters. I suppose several could be set up in this fashion. I am very pleased to have found out how to make use of v3.10b's memory driver!