The memory, which I bought on eBay, was in a box about the size of a toaster. Within the box was a padded mailer that I had to cut open with scissors. Within that was another padded mailer, then the SDRAM module in an anti-static bag. I took the cover off my PC, pulled out a few cables to get at the motherboard, and seated the SDRAM. I plugged the cables back in, turned the PC on and got the message Primary master hard disk fail. After regaining my composure, I checked the cables and found I had somehow knocked the hard drive cable loose. I fixed that, and rebooted successfully. So now I have 192 Mb, upgraded from 64 Mb. Next up: a bigger, faster hard drive.
The room is covered in packing materials, tools and computer parts. I had better grab the vacuum cleaner and tidy up.