Duemilanove vs Uno serial connection

I have two Arduinos. One Duemillanove and one Uno. I am using the Arduino 0021 software. When I try to upload my program to the Uno after using the Duemillanove, I get the error message below. I reset the serial port for the Uno and the Arduino software reflects COM 5 before uploading but the response is that it is searching for COM3 (probably because I just used the Duemillanove). I tried resetting the UNO and closing down and reopening the software but no changes. Any advice?

Binary sketch size: 3098 bytes (of a 32256 byte maximum)
processing.app.SerialException: Serial port ‘COM3’ not found. Did you select the right one from the Tools > Serial Port menu?
at processing.app.Serial.(Unknown Source)
at processing.app.Serial.(Unknown Source)
at processing.app.debug.Uploader.flushSerialBuffer(Unknown Source)
at processing.app.debug.AvrdudeUploader.uploadViaBootloader(Unknown Source)
at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(Unknown Source)
at processing.app.Sketch.upload(Unknown Source)
at processing.app.Sketch.exportApplet(Unknown Source)
at processing.app.Sketch.exportApplet(Unknown Source)
at processing.app.Editor$DefaultExportHandler.run(Unknown Source)
at java.lang.Thread.run(Thread.java:619)
processing.app.debug.RunnerException: Serial port ‘COM3’ not found. Did you select the right one from the Tools > Serial Port menu?
at processing.app.debug.Uploader.flushSerialBuffer(Unknown Source)
at processing.app.debug.AvrdudeUploader.uploadViaBootloader(Unknown Source)
at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(Unknown Source)
at processing.app.Sketch.upload(Unknown Source)
at processing.app.Sketch.exportApplet(Unknown Source)
at processing.app.Sketch.exportApplet(Unknown Source)
at processing.app.Editor$DefaultExportHandler.run(Unknown Source)
at java.lang.Thread.run(Thread.java:619)

You have to tell two things to the Arduino 0021 software: The right COM port and what kind of board you are just using, Uno or Duemilanove.

Go to Tools, Serial Port and Tools, Board

Thanks I was confused because it displayed COM5 so I thought everything was ok. just figured out that I need to SELECT the COM port 5 and have the check in front of the text showing to access the port...Devil is in the details.