Hi i deleted my old administrator account many days ago and now i have some troubles with my computer system.can i get back my old administrator accouunt?

You cannot delete the administrator account. If you are talking about another account in which you were part of the administrator group then it is possible. However, if you have deleted it, then it's gone. You cannot get it back. You can recreate it if you want, however any personal documents that may have been deleted with the account are gone for good (unless you choose not to delete your "my documents" folder, then it will still be there under the USERS directory). Any documents or files that you encrypted with your old username are also gone for good. Sorry to be the bearer of bad news.