What about the set statement? If you drop open your command window and type SET does it show something like:

FOXPROCFG=C:\FPD26\CONFIG.FP

Or, in your CONFIG.FP file you may have a statement (or want to put one in if you don't that says.

SORTWORK=C\FPL && or some directory or other.

It sounds like either the SET or the CONFIG.FP have that extra back slash.

It may also depend on which is the operative CONFIG.FP. Doing a search on my laptop, I found about 5... all legacy files from older DOS apps. I must get rid of those some day.