Apache Server configuration

Hello, we have a reporting php file [login to view URL] in our database we have a large table which containts nearly 6.000.000 records now. Our problem is that, when i open one page in my browser, nobody else can open a simple page like; [login to view URL] unless im finished with my page. It seems that the first page is using all the CPU (but i see %16 usage in Task Manager...) We are using windows server, apache installed on it. I think that there is a misconfiguration on the server side... Or perhaps there is some special coding tips on the php side... Normally we are making a lot of php pages without such problems, but we didnt work on 6.000.000 records before also! So im not 100% sure that if this is a server configuration problem or a software problem.. Can you help? We will give you all remote connection, phpMySQL connection etc...