The Webplayer uses a straight thru 44 pin cable to a 2.5" hard drive, the i-Opener IDE cable has the lines flipped 1to2, 2to1, 3to4, 4to3 and so on.
If you have the double ended ended i-Opener cable (the one you connect the middle pair to the IDE header on the mainboard) you can use it to connect an 2.5" drive if you use the outside pairs instead of the middle and of course be sure that you connect pin 1 to pin 1 of the header (pin 1 on the webplayer is nearest to the processor and the ribbon cable normaly is the side with the red on it).
If you have the i-Opener cable that has the cable lines already switched and crimped with only one IDC header on the end, it will not work with the Webplayer (an may cause bad results, the last few pins on the 44 pin IDE cable carry voltage for the IDE device, getting them switched would not be good).
