I have on a PC and Linux Slackware installed, and have 10 Gb free space...
My question is, can I create another partition of these 10 GB and install Mikrotik OS on it.... ?
If I can, is there anything special and is there any problem with lilo ?

I think you can't. RouterOS will format and use whole disk. Even though you have raid hardisk. But I've never tried before.