1. Set memory for Virtual Machinemore than 1 GB
2. Perform Mac and Windows side disk defragmentation
http://www.xvsxp.com/system/system_tools_defrag.php
3. Set Adjust memory limit from Auto to Manual at Parallels Desktop -Preferences-Memory, and set limit a bit more higher than VM memory
4. Disable Themes in Windows serives.msc stop Themes service
5. If you are running in Coherence, try to switch to Single Window, or lower Mac resolution
6. Some antivirus software can load CPU when Heuristic Prediction is set, or Tamper protection (Symantec, MacAffey), adjust settings to risk you are supposed, high security settings is not always good idea, as it can also affect software running
7. Run msconfig , and disable unneeded startup items
See
http://www.netsquirrel.com/msconfig/msconfig_xp.html
8. Make sure that no VNC,or remote desktop connection is established to Mac, this can slowdown Parallels Desktop
9. Optimize computer experience for best performance
10. Make sure that at least 1.25 GB of Memory is free for Mac OS (it is Total Memory - Virtual Machine Memory)
11. Make sure that at least 2 GB +Virtual Machine assigned memory *2 is available on Mac OS partition where VM is located
