>>BTW, I’m still using 2.0 because I need to convert this application to Y2k, and I don’t want to rock the boat in converting it to FoxPro DOS 2.5. There are some serial communications in this program that are currently working. So I’m going let sleeping dogs lie and use the standard version of FoxPro2.0 and tweak the upper memory area.
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>I remember I've converted from 2.0 to FPD2.6 in one day, actually doing nothing but just recompile. Don't remember having any problems (except from banging my head against a wall for not doing it earlier).
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>As for the (in)compatible memory management in 2.0, there was some obscure bit of text somewhere in the help files, don't remember if it was in 1.02 or 2.0, which said FP was using some memory protocol which was 100% by the book (i.e. MS's specs), but virtually nobody else respected it, so it was quite possible to have some TSR (remember that :) which would be misbehaving and no other program would complain, except FP. This bit of text disappeared in the next version.

Yep - that was the change from the Watcom DOS Extender used for 2.0 that demanded pure EMS 4.0 compliance, not just in the provider, but for anything that tried to use EMS. The later (and much better, at least IMO) Watcom Extender that used the VCPI memory management interface was added with 2.5 - it worked with either EMS or XMS memory via VCPI. There wasn't a need for EMM386 for FP2.5 and later to access memoryabove 1MB, just a VCPI provider; DOS 6.0's HIMEM, and possibly an updated version of 5.0's (I don't remember; it's been a long time since I saw DOS 5!) adhered to the VCPI standard.