Thanks MasterGreen for your reply & reassurance, though I'm still puzzled as to why one can't set both TMP and TEMP environmental variables in AUTOEXEC - there MUST be a reason for this and I'm still a little uneasy at having tricked the system so. Any ideas anyone?
On another note, I DID bump into a unexpected problem and it may be of interest how to get round it.
I have a removable HDD bay that I use for backups of important files onto a couple of smaller removable HDDs. Stuffed one in tonight and lo and behold, my D
drive had become E
and the removable HDD was now E: ! Not what I wanted at all and very liable to confuse Windoze! I'd noticed it before, but it hadn't been important. I knew what was happening - DOS/Windows starts by allocating sequential drive letters to all the primary partitions it finds on all the HDDs there are - when THAT is done, then (and only then) will it start allocating the remaining drive letters to any extended partitions that it finds. "There is one relatively simple way to avoid having this letter-shifting happen: don't create a primary partition on any hard disks in the system other than the first one."
"It is perfectly legal to only create an extended partition on a hard disk, and put all of the partitions in it. The only place that a primary partition is absolutely needed is on the first hard disk, because it is required to boot the operating system. You cannot normally boot from an extended partition volume anyway (although some motherboards may let you)." The solution (easy because they were backup volumes) was to delete the primary partition on the removable drives with FDISK and then create an extended partition and a logical DOS drive within that extended partition. Format the new logical DOS drive and away you go. No more shifting drive letters.
I think NT4 and Win2000 allow you to designate drive letters within the OS itself and apparently Partition Magic can also do the job for you without having to reformat and rewrite all your data.
Finally, putting the swap file on a dedicated drive is something that I've read about and considered, but the little Seagate isn't really fast enough. A fast SCSI drive on a fast FSB would be another matter. I was just idly curious and wanted to find a use for the little feller. Fascinating the things you learn... And several apps that write big tempfiles DO seem noticeably quicker.