My computer is not reading my western digital 500gb external hard drive

Paperdoc

Polypheme
Ambassador
More info, please. Is this a brand new empty HDD? Then maybe it needs to be Initialized. That is, Partition and format. Or, maybe not, if those things are supposed to have been done by the manufacturer so that the unit is "ready to use".

However, if this unit WAS working successfully before and only recently stopped, then you have a different problem, and you need some advice on what to check next to help diagnose.