Yes, that's right folks. What may seem like an obvious step sometimes isn't to our dear VM-Engineers. Before you embark on your P2V quest, be sure to take careful inventory of the physical system. Things to look for is the amount of RAM, processors, disk space and (this is a big one) ... the physical NIC IP addresses.
After you've completed the P2V process, the existing NIC in the physical system will no longer exist ... but the static IP that was originally assigned to that server will still be assigned to the (non-existent) NIC! So you'll have to re-assign the IP to the new virtual NIC installed in the OS (after you've installed VMWare Tools of course). Windows will complain that you're double assigning an IP but you can safely ignore it.
Regarding disk space - take careful inventory of what's actually stored on a volume. Sometimes, it's just faster to tell VMWare Converter to skip the volume all together. Why transfer over data you won't need? You'd be surprised what you can skip when you start looking for things to skip. :)
Otherwise, be sure to size your target VM to match the existing physical server or upgrade the specs (i.e. give it more RAM or disk space).
The one case where I would say it's ok to downgrade a spec is in the CPU. Surprised? Don't be ...
Be careful with the number of processors you assign the VM. Just because the source server had two or more physical CPUs doesn't mean you should assign that many virtual ones. Remember, the more CPUs you assign to a VM, the harder the scheduling algorithms have to work to give your VM those resources. No big deal if your ESX Host has 8 cores and you're only running two VMs. But imagine if you're running 12 or more VMs on that same 8 core host. Scheduling becomes complicated and starts to eat CPU cycles up unnecessarily. I've seen many instances where a virtualized instance of a server with one CPU runs much faster than its dual-CPU physical counterpart!
Now, that said if you are "down sizing" your VM to one CPU and you're coming from a multi-CPU system you'll need to make sure Windows knows this. The system will boot no problem, however you will waste lots of CPU cycles as Windows searches for that additional CPU. So you'll have to change your Computer type (Under the Device Manager) from ACPI Multiprocessor PC to ACPI x86-based PC. I'll leave it up to you folks to figure out if your apps will be affected by a change in processor quantity.
Ok, that's it! Happy VM'ing :)