Partition Magic claims my computer has a partition (named '*:') with the file type Linux.
Now I know this computer never had Linux on it, so I doubt it has a partition in the file system, so what is it? I can't acces it through windows explorer.
Is it a hidden part of XP or some rudimentary rests of ME? It has a few hundred MB free space so I wanna have it, but I don't want to fuck up this pc off course.

It may be something the manufacturer put on it. Dells had something called zztop, and they kept an image of the basic O/S in a hidden partition. You run the program and it copies over the partition image.

It may be something like that.

Partition Magic claims that the last tiime something has been written to it was 15 februari 2004, wich was well after I installed XP.
I don't think the company that put this thing together did something like you mentioned though, but you'll never know. I think I'll just steal most of the free space on that drive, and see wether my computer starts to cry.

If you have system restore on, thats probably what it is.

I believe I switched it off some time ago, so it could be that, but does that mean I can remove it?

I don't see why not.