Thanks for the answer. Sorry if my question sounded confused, I am obviously not a native speaker, but you got it exactly right!
I just was interested if I could hookup my Knoppix Laptop to my desktop machine in case it doesnt work anymore at all. But of course you are right this is more of a theoretical possibility, if it really would happen I probably just would try to boot the desktop computer with knoppix cd or floppy and then get a connection, or if it doesnt respond at all I would just remove the harddisk physically.
As I said I dont really need to do this, I was just interested because I read so much how people are happy to recover data with knoppix that they thought would have been lost, and I couldnt picture how they would do that. But I guess they just booted the crashed machine with knoppix and then hooked it up with another machine...

As for the serial connection I dont think its a problem with neither Linux or Windows, I think its covered in other threads so I dont need any info on that, thanks!