Hello HomerJ,
You can accomplish this by clicking into the system tray in the lower tool bar on the lower right side and find the running application for the QC/ALM server and right click on it and then select the option you would like to perform (Start, Stop, Exit).
If the icon is not within the system tray, then you can perform the following: by looking in the following section to get the issue resolved. Start>Programs>Administrative Tools> Computer Management>Services and Applications>Services and then look for the HP Application Lifecycle Management (HP Quality Center if frunning a version older than ALM 11.0) service that is running. You can then either stop, start, or restart depending on the state the application is in at the time.
I hope this answers your question and helps.
Dan