I think it should be ok with Server 2000 too, as long is all flash is up to date there shouldnt be any issues once logged in, errors normally occur before the test is logged in unless the definition files are corrupted, but the reception server should warn you. We have run close to 50 tests simultaneously and its been ok. Its defo worth doing the testing before hand. We have a set procedure for verifying, unlocking the tests 30 minutes before they start, and issue the students with a log in slip once they have been ID Checked.
We only really took the following steps:
1. Install ESM Server on Server
2. Set up Share and permissions to location of definition files
3. Created a path rule to allow read write access to C:\Program Files\Promissor
Daft I know but also worth checking the version of Administrator and ESM is the latest, depending on how you deploy the package. If its done manaually some machine can easily be missed with updates, the old version of administrator talking to an updated ESM Server will cause issues.