ok, lets start from the top
.
1. Uninstall all drivers for the G25.
2. to go logitech and download latest drivers cause the ones on the disk are normally old.
3. UNPLUG ur G25 from ur computer.
4. Open up the logitech profiler install
5. Read through the welcome and agreement and such.
6. Read through Detection and at some point it will tell u to plug in ur G25 into ur USB port!!!!
7. It will then come up with that stupid green bar, you should of plugged in ur G25 about 1 or 2 steps ago.
8. Click on ur G25 when it finishes and then click next
9. don't touch anything as it callibrates, but read and click ur mouse yes or no.
10. The rest is straight forward...JUST read.
EDIT: LOL, I acutally think I did what Jo53phs did
. Try the way I told u a couple more times, then just hit next after the detection even if it doesn't show up. Then go to controllers and open the logitech profiler. If it doesn't show up then restart ur computer and the G25 should callibrate when it restarts.