As answered by Syed, you can change your port no. for Apache as described.
If you don't want to do so, then you can change the port no. for IIS to run ASP.net.
The Problem you are facing is just because both IIS and Apache uses the default port 80. which causes conflict to run which server.
Hence you have to change the port no. for any one.
check this for changing the port in II6:
Configuring IIS 6[
^]
hope it helps :)