I have two different iTunes accounts on my computer but I can not use them both to download content. When I try to download items including pre-purchased items, I get an error pop-up saying that my computer is already associated with an Apple ID.
MacBook Pro, Mac OS X (10.7.5)
If you've used iTunes Match, automatic downloads or redownloaded an account's past purchases then you will have tied your computer to that account for 90 days : http://support.apple.com/kb/HT4627 - so you won't be able to do either of those 3 things on a different account until the 90 days have completed.
If you can't wait for the 90 days to finish then you can try contacting iTunes Support and see if they can remove the association : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page
My Mac wont accept multiple Apple IDs
