Hello There
Check if you are able to ping the SAP Server from you windows 8 machine. if you are not able to ping try fix that issue first by making the entries in Host and Service file.
Try access the SAP system from your run command ( SAPGUI <HOST NAME or IP > <Instance No >). If you are able to do it.
On the lighter note please check the compatibility.
Good Luck.
Thanks Regards,
Avinash I