The ornamental design for a portablecomputer, as shown and described.
FIG. 1 is a top perspective view of a portable computer of the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a right side view thereof, the left side view being a mirror image thereof; and,
FIG. 6 is a rear view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. Any broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.