Maybe someone else here can find some info on A-Trend for you. I came up pretty short.
This is the only even remotely applicable A-Trend link I could find.
If you do not have a manual you may have to assume a standard pinout and x your fingers.
Per Silencio and asm481, the listed pinout seems to be standard. I have a couple Gigabyte manuals in front of me that agree, though the terminology is a bit different.
1-Power..........2-Power
3-USB Dx-.......4-USB Dy-
5-USB Dx+.......6-USB Dy+
7-Gnd.............8-GND
9-unused........10-USB Over Current
The manual specifically states to be careful with the polarity of the front panel USB connector.
I'm not familiar with the specifics of how USB (either 1.0 or 2.0) communicates. I did once by accident plug serial header into a USB socket trying to add a second serial port. when I applied power I got a big loud POP. Maybe 5 or 10 minutes later the PC decided it would power up again. I felt fortunate that it did. So your caution is well warranted.
Maybe if you really need USB on that PC you could just add a PCI USB card?