Accelerator identity

How is the accelerator identity determined?

I have created two different accelerators, both in the same category, but with different names, descriptions and even homepageUrls. Nevertheless, if I install one and then want to install the other, IE allows me only to replace the previous one. I have even tried to install them from different urls. So what does IE make think they are the same and how can I install both?

Thanks,
Jan

EDIT: When I assign them to different categories, they can be installed simultaneously (even if install and homepage urls are the same). However I believe generating random or unique category for each accelerator is not the intended usage, is it?