The ornamental design for a portablecomputer, as shown and described.
FIG. 1 is a front view of a portable computer;
FIG. 2 is a rear view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a perspective view of the portable computer in opened status; and,
FIG. 8 is a perspective view of the portable computer in closed status.
The broken lines shown surrounding the solid lines are understood to represent the bounds of the claimed design, and all other remaining lines illustrate portions of the computer and form no part of the claimed design.