I want to use FAT32 on an external drive but CACHEF32 gives an error at boot

The default behavior of CACHEF32 (the cache daemon for FAT32) is to abort loading if there's no FAT32 partition found at boot time. So if you're using a USB stick, and the stick is not inserted at boot time, you'll get the error message.

The error is not fatal: you will still be able to access FAT32 partitions, but you will lose some performance on reading from the device.

The solution is to add the "/F" option on the CACHEF32 line in config.sys. This will force CACHEF32 to load even if there's no FAT32 partition found at boot time.

e.g.:
CALL=X:\TOOLS\SYSTEM\BIN\CACHEF32.EXE /L:OFF /F /Q