After upgrading Parallels Desktop to 11, 12 or 13 from earlier versions my 3rd party applications in Windows (XP, 2000, 2003 Server) are very slow.
By default CaParavirtualization mechanism that improves performance for legacy Windows operating systems is disabled on modern Macs.
Enable CaParavirtualization by disabling generic optimization for Windows XP, 2000 and 2003 Server.
- Shut down Windows (Actions > Shut Down).
- Open the virtual machine's configuration.
- Go to Hardware > scroll down to Boot Order menu > unwrap Advanced Settings > copy and paste the following value to Boot flags field: