Windows virtual machine with third party antivirus installed, e.g. AVG, ESET, etc. is extremely slow.
Third party anti-virus programs may block Parallels Tools and thus cause the system to malfunction and attribute to slow performance.
In order to speed up your virtual machine it is strongly recommended to remove any third party anti-virus software from Windows and use Kaspersky Internet Security which has been tested in virtual environment and is shipped together with Parallels Desktop and can be installed from the menu of your virtual machine.
In case if you prefer keeping your current antivirus, you need to add Parallels Tools to the antivirus exceptions list. In order to get more instructions on how to do that please contact your antivirus Technical Support Team.