I'm cross-posting this here from the VCF Forums, because its been two days and I am still absolutely stuck on this. I have a working Microsoft serial mouse that I have successfully tested on my 5155. I have a PCjr. I made a DB-9 adapter for the RS-232 serial port on the PCjr. I plug my mouse in, and the Microsoft Mouse driver recognizes it, mouse test software indicates that it can register left and right button presses, but I can't get the cursor to move! Is there some sort of secret that I don't know about? I've checked my connections with the multimeter, all are good. I'm using a DB-9 male adapter on one end and a 2x4 berg connector on the other end. This is the pinout I am using: PCjr RS232 pinout (direction: you are staring at the back of the PCjr):          1     2     3     4     5     6     7     8      A (XXX) (DTR) (RTS) (TxD) (DCD) (DSR) (CTS) (RxD)      B (GND) (XXX) (XXX) (XXX) (XXX) (XXX) (XXX) (XXX) This is the pinout of the male DB-9 plug (direction: you are staring at the plug):        1         2         3         4         5      (DCD)     (RxD)     (TxD)     (DTR)     (GND)           (DSR)     (RTS)     (CTS)     (RI )             6         7         8         9 Note: Pin 9 is not wired, as RI is not used on a PCjr's RS-232 port. And as far as I can tell, this is what is supposed to be the pinout of a Microsoft Serial Mouse (Female DB-9, direction: you are staring at the plug):        5         4         3         2         1      (GND)     (   )     (TxD)     (RxD)     (   )           (   )     (   )     (RTS)     (   )             9         8         7         6 -- Regards, Dan FitzGerald They/Them or She/Her Classical Computing Laboratory at IBM-Poughkeepsie http://www.vm.ibm.com/devpages/dfitzger