If your presets have the .vpr extension, they are from PPro2 or earlier.
Encoding presets created in CS4 (either AME or Pr) has the .epr extension.
They are located in these two folders:
C:\Users\*yourusername*\AppData\Roaming\Adobe\Adobe Media Encoder\4.0\Presets
Unlike CS4, CS5 uses a single location for the encoding presets:
Copy your presets created with CS4 (both AME and Pr) to the CS5 folder.
If I recall correctly, I had to re-create my .vpr presets from PPro2 to
.epr presets when I made the switch to CS4.