The ornamental design for an all-in-one computer, as shown and described.
1. All-in-one computer
1.1 : Perspective
1.2 : Rear perspective view
1.3 : Front
1.4 : Back
1.5 : Left
1.6 : Right
1.7 : Top
1.8 : Bottom
The present design is for an all-in-one computer comprising of a computer built into a monitor with a Radio Frequency Identification (RFID) module; the RFID module is built in the lower front of the monitor, and it is possible to improve security and convenience by logging in and by tagging a card or the like; the broken lines indicate portions of the article that form no part of the claimed design.