Cool tools; sysinternals
Just this afternoon I was getting upset with Microsoft ActiveSync which had problems synching with my iPAQ 4150. It has successfully synchronized for several months on COM5 (Bluetooth) but this week it suddenly decided it liked COM1 better. I enabled/disabled/rebooted and tried all tricks in the book but no way; after a reboot Microsoft ActiveSync defaults to COM1.
Instead of hunting for random registry keys I fired up RegMon (no installation required) and opened ActiveSync. A quick search in the recorded results and I found the offending registry key:
HKEY_CURRENT_USER\Software\Microsoft\Windows CE Services\SerialPort
I changed the value to COM5 and it works like a charm!
Most of the utilities come full source and I don't know what I would do without them.