vCenter server can be installed only on server OS with 64 bit and not on Client OS. Below are OS on which vCenter can be installed
Check Minimum system requirements for installing vCenter Server
Thank you
As this Vcenter 5.0 requires 4 GB of memory, can i use the older version of the Vcenter for the Esxi 5.1 hosts
As this Vcenter 5.0 requires 4 GB of memory, can i use the older version of the Vcenter for the Esxi 5.1 hosts
If you want to use ESXi 5.1 you would need to install vCenter 5.1 . Check VMware Product Interoperability Matrixes
I hope you are planning to test vSphere, if this case you can use VMware Workstaion and on top of it you install ESXi provided your hardware support.
Check Building the Ultimate vSphere Lab as sample