It is not easy, as my laptop runs Intel 82579LM network card. Intel 82579LM is not a supported NIC so ESXi 5 refused to install on it.
The fix is to integrate the network card drivers onto the installation media.
First, you need the ESXi 5 installation media. This is easy, just register and download from VMware website. They offer this free of charge (for basic hypervisor features), or 60 days free evaluation.
Second, you need 82579LM network card drivers. You may found this website useful.
Third, you need an integration tool (this save a lot of time). I found ESXi-Customizer.
Building a customized ESXi 5 installation ISO is not difficult with these three things together. Finally able to install ESXi5 on my 32G RAM Lenovo W520.