The ornamental design for a windowcover, as shown and described.
FIG. 1 is a front, perspective view of a window cover showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view of a second embodiment of a window cover shown with break lines, that being the only difference from the embodiment shown in FIGS. 1-4 and 6-7, the break lines symbolizing breaks in the length of the article in which the claimed design is embodied, the appearance of any portion of the article between the break lines forms no part of the claimed design;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is top plan view thereof; and,
FIG. 8 is a front elevational view of a third embodiment of a window cover shown with break lines, that being the only difference from the embodiment shown in FIGS. 1-4 and 6-7, the break lines symbolizing breaks in the width of the article in which the claimed design is embodied, the appearance of any portion of the article between the break lines forms no part of the claimed design.