Asp.net Problem Plz help Urgent!!

Hi,
Can anybody help me?
My problems are...
1. I am developing a web application using asp.net,but when I wanted to distribute some works to my friend then I am facing great problems.
Firstly he is developing some pages in a different computer.When we are trying to merge the web forms its showing an error.
Plz suggest a way to share work while using asp.net

2. when I am trying to run the web application in a different computer its showing error.I have tried the install package also,but failed.
What i am doing is -I am creating a virtual directory and linking the folder.
But its not working...Plz help

3.IN one of my client's computer when I tried to install .net and tried to run asp.net its showing error.
IIS and Sp4 also already installed ....
These things are making me crazy....Plz help me