To install ReSharper 4.5:

1. Exit all running Visual Studio instances
2. Run the ReSharper 4.5 installation.
3. On the first installation page you will be prompted which version of Visual Studio to install ReSharper for. Choose appropriate version and proceed with installation.
4. Launch Visual Studio.
5. You will be able to evaluate ReSharper for 30 days for free or enter your license data. ReSharper edition will be determined from your license key.

Special notes:

If you have a ReSharper build installed which is earlier than 3.0, follow these instructions:

1. Uninstall your previous ReSharper version.
2. Reset all settings (via Tools -> Import and Export Settings -> Reset all settings).
3. Exit all instances of Visual Studio.
4. Install ReSharper 4.5.

Develop with pleasure!