1. You didn't write what you were doing when the no memory available message popped up. A common ill is Microsoft Word. Renaming the NORMAL.DOT fixes that, but without your info, simple fixes are going to be missed.
2. "how do I figure out what they are" ?
http://www.google.com Hint: type in the name...
3. "how do I clean it up to have only necessary programs running."?
The cleanup varies. If you find some PEST or PARASITE then you deal with that. If its some optional startup item, then I note STARTER at the Anti-Patasite Suite. Before I note the usual words, be sure you haven't simple filled up the hard disk.
http://reviews.cnet.com/5208-6132-0.html?forumID=32&threadID=1313&start=0 notes the five scanning tools and removal tools that are fairly safe. If one does encounter an issue, its always been damage done by the MALWARE. The most common issue being Layered Service Provider replacement which you can use LSPFIX (Hint: use http://www.google.com to find).
The thread has follow on discussions about new links if you don't want to use Google to find an item.
PPS. All the tools are free.
I use Windows ME and upgraded my memory to 256- I still will have one or two windows open and receive a no memory available message- when you press alt ctrl del there are about 20-30 programs runnung- only a few that I can identify- how do I figure out what they are and how do I clean it up to have only necessary programs running.