http://www.javaop.com/~joe/VB6/SystrayUptime.zip
Source and binary included.
This does some nifty little API calls and makes a tray icon. It displays the system uptime (now "System uptime: 4 days, 1 hour, and 40 minutes") to minute precision as the toopltip. I had it to milisecond precision, but when you moused over it, it was gone before you had the chance to look at the tooltip (it deletes+remakes). Anyhow, it updates every 30,000 miliseconds (30s).
Its a set it and forget it program. No message boxes, no ugly form (shown =p). Stick it in your startup folder and enjoy!