The Mac's present slowness is almost undoubtably attributable to the quality of housekeeping by former owner(s). The file directory and files on the drive have the potential, after umpteen years, to be considerably fragmented if no attention has been paid to that. NUM (Norton Utilities for Mac), although I do not know which version is necessarily the best (it will be 3.2 or lower) will defragment and optimize the drive at the same time as it sorts the file types into directory, System, CPs, Extensions, documents and so on and reassembles the fragments contiguously. That will save the SE a lot of thrashing of its HDD during loading of the far-flung fragments of files into memory, and consequently, much time in doing so.
If you have the means to do so, merely copying the contents of the drive to another drive, and then back again, can achieve the same effect but at the cost of more time and two transfers.
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