MC5 installation

i'm having some problems with the installation of MC5.  when  i open a file it says that it has a problem opening it, but i opens anyway.  additionally, i wasn't able to open bundles from MC3 that i saved on a CD, it says that it needs plug-ins.  ???
 
i've noticed that MC5 is not in the list of software where all the other programs are listed.  i unistalled and re-installed the program before, but not being computer savvy i wasn't able to help anything.
 
any ideas?  i'm not sure what i'm suppose to write to be more specific about this. i just have the vague awareness that something is wrong, but don't know what.   please ask me questions. 
 
thanks,
sirena del mar

you do have me confused with someone else.    i had MC3 in the previous laptop and installed MC5 in the present laptop.
 
yes, i installed MC5 from a CD.  there's a window that comes up during installation that asks where do you want the different aspects of the CD installed, i let the defaults choices.    i don't know enough tech language to know what to write or change it to.  (OMG, i just finished a sentence with a preposition!!  does that means i'm going to language hell?  )
 
when the Missing Plug-in windows comes up it lists the audio files not the midi or fx.  the projects do open, but there's no sound from the audio files. yes, i know that it sounds wack, but there it is. 
 
ask me more question please.  i lost the previous laptop when i was about 20 minutes to finish the project i want to finish now.  i feel a bit histerical that this isn't going smoothly.  my hand keeps wanting to go to the panic button and i keep pulling it back, hoping that someone would give me an idea that can save me as i don't know enough computerize to save myself. 
 
(do you now if i could install MC3 in window 7?  i could finish the project and then re-install MC5.  is this a good idea??)
 
sirena del mar 
 

i'm still confused about MC5 installation and i don't know if i should start a new thread or use this one. 
 
first, i discovered that the files i had saved from MC3 were corrupted and i couldn't open them.  i think that the previous laptop started malfuntioning before it broke down and i didn't notice it.  i lost a lot of material that i'm working in reconstructing even as i write this.
 
now: shouldn't MC5 be installed in the computer's memory, that is, Windows (C):?  mine installs where i keep my files, under Documents.  then the Cakewalk Projects folder, that i believe should be in my Documents folder, show up under Windows (C).  when i want to open MC5 from the project, i have to open Windows, find the Cakewalk Project folder and then open the project.  since no other software does that, i think it's odd,  but maybe i'm wrong.
 
i also cannot find the folders for the loops in the loop explorer.
 
i re-installed it MC5 today, i had installed MC3 in an attempt of saving the files i mentioned before, and i didn't find any place where i can select for the folders to installed differently.
 
as always thank you for any help i may get,
sirena del mar