Poor performance from vb.net

Question

Help, I've developed a system using vb.net but the performance is so slow that it take almost 3 minutes just to load the log-in screen. The system contain around 150 forms and tens of crystal reports. This is the first time I am using VB.net and I have zero experience in vb programming. My guess is that the system is using too much memory as the whole system is under 1 exe. What can I do to breakup the system into smaller chunk? Thanks.