There shouldn't be a problem with another USB providing you have the ports. Parallel would be fine too.
Once installed you choose which printer is to be the default printer (printers folder - right-click on the printer icon and and select 'set as default). When you choose print from the file menu in your programs you can choose which printer to use from the drop down menu in the print dialogue - the default will be first in the list.
When you save a document in some programs it saves the print settings aswell and will print to the printer you chose when you saved it.
Good luck - but there should be no problems.