Havn't tried this personally, but I've heard it works:
Stop update manager service
Copy everything from c:\Documents and Settings\All Users\Application Data\VMware\VMware Update Manager\Data to your new directory
Edit c:\Program Files\VMware\Infrastructure\Update Manager\vci-integrity.xml file
Change the following two lines to point to your new destination
<path>C:\Documents and Settings\All Users\Application Data\VMware\VMware Update Manager\Data\</path>
<patchStore>C:\Documents and Settings\All Users\Application Data\VMware\VMware Update Manager\Data\</patchStore>
5. Start update manager service