MSDE Questions

I just installed .Net Enterprise Architect version and was given the option of installing the SQL Server Desktop Engine, which I chose to do. Others I have spoken to were able to install the full blown SQL Server that includes useful apps like the Enterprise Manager. Why is it available on some installations and not others? Using the MSDE through VS.Net I am able to access databases, but if I try to access the same database through MS Access, I am unable to login in to the server. If I try logging in using a trusted connection I get an overflow error and I can't login using SQL security because the "sa" id is not recognized and I can't change the id or passwords because I don't have the Enterprise Manager. It's all very frustrating. Any help would be appreciated. Thanks