EXE files dont know how to open. things try to open in DOS?!?

[NeedHelp?]

Ok, I am stuck! please help.. it all started when i was messing around in comand propt. i typed 'help' then typed 'more' but w/e.. after that a few files were trying to open in dos. the dos window would appear then disappear in a second. i was like "***!?" so i did a system restore but that didnt help, i looked on a forum and saw someone had the same problem "EXE files open with dos" someone said to go into folder opions then look under the EXE extension and delete it if it said it should open with dos. i looked but it didnt have the exe extension, i thought that might be the problem so i made one. after that any exe file now says, when i open it, "windows cannot open this file, to open this file windows need to know the program that created it blah blah etc. what do u want to do? open it using the web, open it using a list of programs" im like OMFG!!!!!! please can someone help!!!

PLEASE!!!!!!! HELP!!

[NeedHelp?]

Edit: Ok, i downloaded something that fixed the exe thing, most exe files work now. but ive still got the same problem i started with, Some exe files and other files try to open in dos. does anyone know how to fix this?

It seems if i reinstall the program that is trying to open in dos then it opens normally. but i am trying to open steam (counter strike) and i cant reinstall this program when i do this is what happens:
it starts searching for installed applications then a window pops up "Error 1327. Invalid Drive I:\" (Lol the error nearly says "1337" :P) But i dont have a drive I:\.. altho i did have one but i disconnected it agers ago. i did install steam on I:\ but also on D:\ but maybe because C:\ has been the main drive (system drive) for when both I:\ and D:\ where available it thinks its installed on I:\ instead of D:\ but i dont have an I:\ so i cant uninstall, when i try the same message appears as when i try to reinstall lol... can anyone help?