I am going to assume that you are using this tool: http://forge.ow2.org/projects/javaservice/ (many of the tools that turn Java apps in services have Java Service as part of their name so it is often impossible to tell which is being used just from the name)
This tool uses a registry entry to hold the run options. Look at the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
XXX\Parameters, where XXX is the short service name. To add additional JVM options, edit the "JVM Option Count" value, and than add an additional "JVM Option Number X" item, where X is the next number after the existing ones.
the service was setup with the JavaService utility (part of an Adobe Lifecycle installation). will check out the registry entry (would have never guessed going that why....thanks for the tip). assume i can see every argument to the jvm in the register.
best alternative in the future might to reinstall the service with my settings. will respond back later with a solution.