Well, I managed to install and use HTC Sync on Windows XP x64, which I consider the best performing Windows version ever made yet.
Here are the steps to do this:
1. Run installer package from HTC web site. I used "_HTC Legend_HTCSync.exe" v.2.0.33. While it is running copy "HTC PC Suite.msi" from your temp directory to a separate location.
2. Use Orca MSI editor to make the following changes:
- disable Windows version check: remove "And (Not VersionNT=502)" from LaunchCondition entry
- disable driver installation step: set condition InstallUISequence\CA_DriversInstall to a value that evaluates to False, e.g. "0 = 1"
3. Install the MSI package as modified at step 2. It should install correctly.
4. Manually install 64-bit Vista drivers for HTC communicators. They install just fine on Windows XP x64. I used the drivers from the following page:
HTC Hero Drivers download for Android - Softpedia