Okay I have downloaded sacred east and its mixed with the other tow maps so, I seen if you install this it will replace tr.bsa tr_esm , if I do this will it ruin anything for my game? I simply want to try this and wanted to see if I overwrite this to replace files will it affect anything?

Will it affect anything? Yes, your Load Order and your game

Update your Load Order accordingly with Wrye Mash, (deactivate the old, activate the new, update masters) then update/repair your save file as well, if you're using a current save.
Same as any mod

Okay because I thought if I overwrite the old files my whole game would be corrupted so my problem is if I download this will only map 4 be available to view or are the other maps still available I know you have to start a new game. So you mean activate the other Tr.BSA and TR_ESM and I uncheck the old version of that, so do I just replace the file to do all of this?

Don't replace the latest FINISHED mod's data with the old data from a BETA.

Just use the map 4 .esp, not it's bsa and data.esm, because the newer maps will have things missing, won't they?

I thought the 4 Beta was all of the released content, plus some extra Beta stuff.
If that's not true, sorry, I just assumed that's how it was packaged. (I haven't installed it yet)

Ezio, you can always make multiple saves with different load lists, so that might be your best bet here.
Or, as many of us do, even use multiple installs.

Sorry Pluto, that was aimed at Ezio, oops. The 4 Beta came out nearly two years ago, so it's bound to be missing newer models/fixes (I know it will be missing the 7 or so models I had not yet made )

Using the esp does not work, I loaded a new save game and still nothing of this.

I'm still a little bit confused what multiple morrowinds? Or on otherhand multiple map 4s which I know that does sound silly. I just used the esp and tried to find kartur and nothing happened.

I was thinking of the Download link half way through the OP http://www.gamesas.com/topic/1360769-wip-tamriel-rebuilt-sacred-east-4/
Which I just now realize is much older than I thought it was.

(unless there's also a newer Alpha that Ezio means)

But that link is now very outdated, and probably will not work alongside Sacred East at all.

You can install Morrowind as many times as you like, moving it to different File locations that act separate from each other.
This lets you have different mods on different installs. This is good for avoiding mod conflicts, or just building different "versions" of your modded Morrowind.