You might try doing the reset with access doors closed. When you plug the power cord back in, you could unplug it once you hear movement in the printer. Sometimes there is enough movement during startup to unlock the carriage. If it did move far enough ( I wouldn't force it ), you could move the carriage to the middle and do Solution 4 of the Carriage Jam document. You could also have a better look on the other side of the carriage to see if there is any paper there.
If that doesn't work, you could try downloading and running the HP Print and Scan Doctor for Windows. Does that help?