Spectrum database directories should be excluded from virus scans, backup software and any other 3rd party software.
Virus scan software and backup software specifically can cause issues with database reads/writes by corrupting the data. Accessing the database files while the database engine attempts to write to those files will cause problems.
The following directories must be excluded from virus scans or any other software that accesses database files:
The official word from MySQL about excluding their database files:
Using virus scanning software such as Norton/Symantec Anti-Virus on directories containing MySQL data and temporary tables can cause issues, both in terms of the performance of MySQL and the virus-scanning software mis-identifying the contents of the files as containing spam. This is because of the fingerprinting mechanism used by the virus scanning software, and the way in which MySQL rapidly updates different files, which may be identified as a potential security risk.
After installing MySQL Server, it is recommended that you disable virus scanning on the main directory (datadir) being used to store your MySQL table data. There is usually a system built into the virus scanning software to allow certain directories to be specifically ignored during virus scanning.
In addition, by default, MySQL creates temporary files in the standard Windows temporary directory. To prevent the temporary files also being scanned, you should configure a separate temporary directory for MySQL temporary files and add this to the virus scanning exclusion list. To do this, add a configuration option for the tmpdir parameter to your my.ini configuration file. For more information, see Section 2.9.7, "Creating an Option File".
Text taken from: http://dev.mysql.com/doc/refman/5.0/en/windows-installation.html