If the ONLY problems are "Incorrect DOS Version" messages, then you can still use 6.22 . That's what SETVER is for. Somewhere in the code that you are running is something that closely resembles: MOV AH, 30h INT 21h CMP AX, ... That inquires of the OS what version it is, and then balks if it isn't what was expected. SETVER, which started with version 5.00 (?) lets the OS lie about its age for just that situation. SETVER contains a database that is configurable via the command line, so that the OS can keep its lies straight. You'll need to install SETVER and add entry to its database. 3.30 and 3.31 are significantly different. Among other things, 3.30 can not comprehend a drive (lofical or partition) larger than 32 honest megabytes (it is limited to 65536 sectors per drive). 3.31 can go to 2 honest gigabytes (if the BIOS can handle it). 3.31 and 2.11 are the versions of MS-DOS that are HEAVILY customized - besides MODE.COM being unique, they often have had hardware vendor added support for unique hardware. Compaq MS-DOS 3.31 is different from Zenith MS-DOS 3.31, etc. BTW, there is no PC-DOS 3.31, unless you want to count 4.00. BTW, there is no such thing as 3.3 !! INTERNALLY the OS version number is stored as if it were a 2 digit decimal number. Thus, 3.30 INTERNALLY is 3.1D or three point thirty, and 3.31 INTERNALLY is 3.1E or three point thirty-one. Thus, if there WERE a three point three, it would actually be 3.03. If you have difficulty configuring SETVER, among us we can probably come up with 3.30, and haf a dozen varieties of 3.31. Good luck, -- Fred Cisin cisin(a)xenosoft.com XenoSoft http://www.xenosoft.com 2210 Sixth St. (510) 644-9366 Berkeley, CA 94710-2219

Hello all, I have just acquired a PC-based instrument. It's a Model DTA 8850 Digital Timing Analyzer, made in 1989 by a company called International Test Instruments, Inc. in Irvine, CA. Unfortunately, they seem to be out of business. The machine is based on a PC architecture, with the specialized signal conditioning circuitry on a backplane. It has some sort of non-volatile electronic disk as the C drive. I was able to determine that the operating system is DOS 3.3, but there is something munged about it, because it won't run the application software for the instrument. I can boot the instrument from a floppy, but the only version of DOS I have is 6.22, and the instrument gives "Incorrect DOS Version" error messages when I run the application software (but it does run). I would like to get a copy of DOS 3.3 to restore this machine to its original state. Also, does anyone know anything about International Test Instruments, or (fingers crossed) have a manual or other information about this machine? Thanks in advance, Stan