The problem you have is that there are 3 different 8mm formats (possibly more but I only know of 3) and all use similar tapes that are of exactly the same size.
The older 8mm format (analog)
The newer Hi8 format (again analog)
and Digital 8mm format (Digital)
Most of the time you cannot use the tape from one sort in a different sort as the formats are not compatable.
I have a Hi8 and Digital8 camera here and I can use the Hi8 tape in the digital camera to playback BUT it will not output to a PC because the tape was not recorded in the digital format. You could use a capture card to capture the video but it is not as easy as copying from a digital8 tape. Again, this is my video camera here that I bought specifically to allow playback of older 8mm tape formats and I believe most Digital8 cameras will not allow you to do this.
I think you are going to have to borrow your friends camcorder and obtain a video capture card so you can copy the anolog tape onto your PC.