I know you said you don't wanna track down an old AIM version, but if you give up there's
http://www.oldversion.com with old versions of AIM on there.
I personally use AIMutation, sans any system-slowing skins provided. Works great, I've had it on my systems for 6+ months and I can look up logs from last May. The only problem that I can't seem to get around is that to view the logs (without using explorer to dig up the files/folders) is that you have to be signed into AIM to look at the logs.