#1 - Aug. 27, 2010, 5:33 a.m.
There are a variety of subscription options after your free time has run out, Aquriah. The most common is the 14.99/month option, though we do offer discounts for more time subscribed at once, as well as pre-paid game cards. So long as you add a subscription to the account you currently have upgraded to Burning Crusade, you won't lose any characters. =)
I do see you have created a number of other trials - each time you create a trial, you will default back to only the normal, original game access, with no characters, and have all the trial restrictions, as these are all separate game accounts. It would be best to consolidate your purchases onto just one World of Warcraft account, so you can get the most out of the characters you create there.