>FoxPro / FPW may temporarily use 2 or 3 times the actual size of the file(s), I think, for certain commands. Check the files in your %TEMP% folder while the query, indexing, etc., runs, to see what happens.
That's an excellent suggestion, and we did try that. When we pointed the SORTWORK and TMPFILES to the alternate local drive we didn't see anything unusual. The SQL generated some TMP files, but nowhere near 850 MB. However, when SORTWORK was pointed to C:\TEMP the TMP files are about the same size, but eventually we run out of disk space. It feels like NT and FoxPro are fighting for diskspace, but Foxpro loses the battle.