I repeatedly find that WSS_AdminService.log is reguarly a source of problem on the SharePoint servers that I work with. The problem is that this file gets written to every minute and it keeps growing and growing and there doesn't appear to be any known way to tell SharePoint to truncate it or purge it like normal logs. I examined the contents and there appears to be no valuable information in it compared to the regular logs in the 12 hive. At one point, this log file on one of my servers had grown to be over 1 GB. This can be a real issue on a virtual machine you use for development since you don't always have a lot of disk space available. The file can be typically found in the location below.
C:\Documents and Settings\Default User\Local Settings\Temp\WSS_AdminService.log
You may want to rename it, move it, or do something with it, but I usually just delete it. It would be nice if SharePoint would take care of this file for you, but for now it looks like you are going to just have to take care of it manually or write a script to delete it periodically.