Serial port wont work for multiple PC's

We are trying to connect a Sharp 2Y0A02 with our arduino uno board, but every time we go to upload the code we get this error. We thought that maybe it was something wrong with the sensor but we tried multiple sensors and nothing worked. We looked online to see how to fix this and tried going Tools> Serial Port, but the serial port is greyed out and we are not able to click on it. Any suggestions?

This report would have more information with
“Show verbose output during compilation”
enabled in File > Preferences.
Arduino: 1.0.6 (Windows 7), Board: “Arduino Uno”
Binary sketch size: 2,708 bytes (of a 32,256 byte maximum)

processing.app.SerialNotFoundException: Serial port ‘COM3’ not found. Did you select the right one from the Tools > Serial Port menu?

at processing.app.Serial.(Serial.java:191)

at processing.app.Serial.(Serial.java:77)

at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:77)

at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:175)

at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)

at processing.app.Sketch.upload(Sketch.java:1666)

at processing.app.Sketch.exportApplet(Sketch.java:1622)

at processing.app.Sketch.exportApplet(Sketch.java:1594)

at processing.app.Editor$DefaultExportHandler.run(Editor.java:2382)

at java.lang.Thread.run(Thread.java:619)

That sounds like you have not got a serial port driver loaded. What happens if you connect the Arduino board without the sensor connected?

Also post a link to where the boards came from so their specifications can be checked.

we got the boards from http://www.robotshop.com/en/arduino-uno-usb-microcontroller-rev-3.html and thene we tried loading the serial port driver and got it to work when we ran the sample blink code, but once we tried to upload anything else we got that error.

The board will have the blink sketch loaded by default so it is possible that you have not uploaded anything.

Check which ports are available in the IDE with the board disconnected and connected. The one that appears when connected is the one you want.