Fact is that Toshiba doesn’t support Linux OS for this notebook model so with all this you are on your own.
I recommend you to visit some Linux forum and try to pick up some useful info from there. Maybe you will find there other people with the same notebook who want to install Linux.
Portege's are, in my experience, hot machines. The cooling modules is on the very limit of being able to cool the system effectively. I have seen quite a few issues with Linux and this series of notebook with the latest Kernel version. I can only suggest using the downgraded version until more support is either available from Toshiba (highly unlikely) or the Linux Kernel.