If you research the tool BELARC ADVISOR it can list the make and model of the existing drive as well as other machine and software details. Armed with the drive make and model you could answer the question about SATA.
Does the NB255 use a SATA hard drive, I think it does ?
And is there a limit to hard drive capacity on the 255 ?
I might try a 500gb HD.
Also, HD thickness ?