I have a quick question for anyone who's experienced, lol. Ok, I have a PS2 optical mouse. The wires inside go:

GREEN>BLUE>ORANGE>WHITE

I have a USB cable from a USB optical mouse that got trashed awhile back. The wires (of course) are

GREEN>WHITE>RED>BLACK>BLACK (ground)

I want to replace the PS2 cable with the USB one. So... which wires do I connect to which? I'm fairly certain white goes to white (and pretty sure the green goes with green too), lol, but the rest idk. Any help will be massively appreciated, thanks!

Thanks for the help.  I'm checking it out right now :)

Well, the 2 reasons I can't use that adapter are 1. I can't afford to purchase one, and 2. this is for a mod anyway, so why not start there?  lol
 
Anyway, thanks to the quick response of bighairycamel, along with some additional searching I did (gotta love wikipedia, etc.), I came up with this as what I need to use for connecting the wires:

 
I drew it out on paper, then re-made it in mspaint.  If this does work as everyone said it will, then I think I'll also possibly apply this to the keyboard.  I'll keep ya posted :)

You have your USB pins laid out backwards... Check this out.  With the USB connector facing you (cable going away from you), the pins go 4321 from left to right.
 
EDIT:  My link is the same that bigharycamel posted.  Don't go by color, go by pin placement.

The lineup of the colors on the USB side isn't what matters, as long as they're connecting to the proper wires on the PS/2 connection.  I know that I switched the green and white in my pic, it's not a big deal.  The green still connects to the white and the white to the green.  Regardless, with the mouse I tried, it didn't work whether I did it that way or connected the white to white n green to green.  Either way, it didn't send/receive any data transmissions.  The sensor would illuminate the led, and it'd dim/brighten appropriately, but wouldn't register data to/from the port.  Oh well.