If you don't own homelab or Powerfull PC, or you cannot break production environment (obviously in most cased you can't) you have another option to prepare for your VCP exam. This offering is called VMware vSphere: Install, Configure, Manage [V5.5] – Lab Connect allows to get 30 hours of preconfigured lab environment Online.
The lab environment consists of 24 labs:
• Lab 1 – Installing VMware vSphere GUIs
• Lab 2 – Configuring VMware ESXi
• Lab 3 – Working with Virtual Machines
• Lab 4 – Configuring VMware vCenter Server Appliance
• Lab 5 – Using the VMware vSphere Web Client
• Lab 6 – Configuring VMware vCenter Single Sign-On
• Lab 7 – Creating Folders in VMware vCenter Server
• Lab 8 – Standard Switches
• Lab 9 – Accessing iSCSI Storage
• Lab 10 – Accessing NFS Storage
• Lab 11 – Managing VMware vSphere VMFS
• Lab 12 – Using Templates and Clones
• Lab 13 – Modifying a Virtual Machine
• Lab 14 – Migrating Virtual Machines
• Lab 15 – Managing Virtual Machines
• Lab 16 – Managing VMware vSphere vApps
• Lab 17 – User Permissions
• Lab 18 – Resource Pools
• Lab 19 – Monitoring Virtual Machine Performance
• Lab 20 – Using Alarms
• Lab 21 – Using VMware vSphere High Availability
• Lab 22 – Configuring VMware vSphere Fault Tolerance
• Lab 23 – VMware vSphere Distributed Resource Scheduler
• Lab 24 – VMware vSphere Update Manager
Unfortunately there is a price to pay, but in some cases it might be also a time saver as you don't have to create the environment and you can directly go exercises through the labs.
Check out this page for more details and pricing. One must count around $400 for 30 days, during which time the lab environment stays available for your exercises. This training environment does not replace a VMware obligatory class, which you must attend in order to get certified. Register here.
If you don't like paying for online labs, than I would suggest going nested way. Either through VMware Workstation installed on the top of an existing OS on a PC or Linux, OR, built a whitebox. In both cases you can build an environments with some nested ESXi hosts, vCenter and the backend network services like AD, DHCP, DNS….
There is many online tutorials how to build a vSphere lab. A way back I've done a step-by-step PDF guide on how to build a nested vSphere lab on a PC with limited resources. Check out this post.
Alternatively: add the Project Autolab at labguides.com/autolab/ a nested vSphere Lab. environment with the minimum effort