Can I continue with my Guild Wars Free Trial?

Once I get the Access Key from playing the Guild Wars Free Trial, can I continue to use the access key that is given to me and play the game when I buy it so I can continue with my initial character from my free trial account?Can I continue with my Guild Wars Free Trial?
Absolutely. You add the access key (giving you unlimited playtime) to your existing account (which right now has the trial key only), but nothing in the account changes - your characters remain, your progress is the same, everything. If you buy other chapters or the expansion you can add these to the same account as well, and just keep playing.

Edit:
If you have downloaded the free trial client and used the free trial access key and then buy the game you will get a full account key. This you apply to your account, and continue playing, using the same characters.
A free trial key can only be used once, and once it expires you can no longer play. However, the characters remain, and whenever you get a full account key you can apply it to your account and continue playing.
You cannot use the same key twice.

Suffice it to say - if you have played using a free trial at any point and know the login to it, and buy the game, you can continue using the same characters/progression.
Hope this straightens out the question.Can I continue with my Guild Wars Free Trial?
Let's start at the beginning... to play Guild Wars, you create(d) a new Guild Wars account on which you log in (using your email address and password). Then you add the trial Access Key to that account, which allows you to play for a certain number of days. You can then create one or more characters, log into the game and play.
After the trial period, the trial access key becomes invalid, but the account (and everything on it) will still exist... and you will still be able to login to the main page of that account, you just cannot cannot play anymore until you add another (valid) key from the retail (or digital purchase) version. You can add several keys to the same game account (for example from different campaigns, or bonus content), and each key that you add will give you access to more content in the same... for the same character(s).
So once you receive the purchased version, all you need to do, is login to your existing account and add the access key from that purchased version to that account. That will unlock the game (and everything on it) again for you to play, and you will be able to continue exactly where you stopped during your free trial, with the character(s) that you created during your free trial. You do not have to reinstall the game using the retail version that you buy, you do not have to create a new account and start from scratch, all you need to do is add the key from the retail version to your existing account. You could compare it to adding prepay credit on a mobile phone... once your credit runs out, you add a new key to your prepaid account to charge up the balance, but you keep the same phone, the same network and the same calls history.

I hope that makes it a little easier to understand.