It turns out that the deficient memory is not the computer's RAM but Xtree's buffer. When Xtree logs a disc, it memorises the directory in a buffer; you can see the size of this buffer if you load the program using a switch, XTGOLD /XM. Its total size is a little over 14 Kb, but with my two hard disk partitions, containing some 7000 files, logged this was reduced by about half. It is evidently this memory that Xtree uses when loading graphics files, and 7K is not enough for a .DWG file.
The solution is to minimise the directories logged by Xtree. First of all, release all disks except that containing the graphic, using Alt-R. This will usually provide enough memory, but more can be released by restricting the current directory to the first level only. This is most readily accomplished by going to the directory window, keying Home to highlight the root directory, and then keying -, then +; use the grey keys on the numeric key pad for convenience. Alternatively, key Alt-L O. You can then move to the main directory containing the graphic file and log to the second level by keying + again, or log the whole branch by keying *. When you have found the appropriate file, there should now be enough buffer memory to permit normal viewing.
Tom Ruben