if you trust me 😉 try out the "HQAgentServiceWrapper". Download the zip-File attached to this posting and extract it to your HQAgent-directory on your Windows 32-Bit Platform. It contains scripts for installing/uninstalling HQAgent as a service and an alternate startscript. Before starting HQAgent by running HQAgent.bat edit "wrapper.java.command"-line in conf/wrapper.conf and let it show to your java-command. For more information read http://wrapper.tanukisoftware.org/doc/english/introduction.html
Not sure if you ever fixed this, but I had the same problem on my Windows servers. It turned out that I had to first set the JAVA_HOME environmental variable before getting the agent to stay running. Java doesn't set this environmental variable when it is installed.
I think this is somewhere in the Hyperic documentation, but is not in the Quick Start guide.