The ornamental design for a computerprinter, as shown and described.
FIG. 1 is a perspective view of a computer printer, showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a left side elevational view thereof (and also a mirror image of the right side).
The portions of the computer printer shown in broken lines on FIGS. 1, 2, and 3 are for illustrative purposes only and form no part of the claimed design.