Extreme Pro as a 2nd HD

Just installed an Extreme Pro 240 on an HP Envy. The system behaves weird, cant restart, have to force shut down. Extremely slow when Accessing This PC . After all this system seems to work fine, apart from those issues. One time my log in screen locked up. Also, the Sandisk Dashboard 1.4.2 does not recognize the drive at all. It recognises my Sandisk for the C drive, but not the new one on E drive.I have a Sandisk 240 extreme on c drive; SATA0, which is the only 6gbps port, the others are 3gpbs but that should cause the issues should it? 

No, Extreme Pro would still work on a SATA 2 port but with limited performance, in your case please contact our support center and give us more detailed information so we can better assist you.

Try reinstalling the drivers. The drive should work fine. If it is slow that must be because of corrupted driver or some other problem.

Please run the disk cleaner tool and also check if dskmgmt is showing it.  If all fails you will have to contact support.