Is there a way to mass export ALL contacts on iCloud (on PC)?

Log into iCloud.com, open Contacts, then click the gear-shaped Action menu icon at bottom left, click Select All and then using the gear-shaped Action menu icon click Export vCard.

Try clicking again. Same thing happened to me when I tested it for the above response. It worked on the second try for me. On my Mac it automatically put it into the Downloads folder. On a Windows PC I'm not sure if it will prompt for a location or just put it somewhere. If nothing happens after you have clicked several times try searching for the file on your computer. It will be named <first contact name> and xxx others. Try a search that includes just the first or last name of the first contact.

That is likely because they are formatted as vCard. To my knowledge that is the only format that they will export as and most other address books/contact applications should be able to handle that. More information on vCard: http://en.wikipedia.org/wiki/VCard