Could any one clarify me the difference between the Computer Validation and Software testing?
Do you mean software testing as apart of the overall validation, or software testing in terms of application development. These are two entirely different things.
Computer Validation or Software Validation is what I think you mean is ensuring that all operational/functional aspects of the software have been tested either as part of a FAT/SAT/OQ in relation to the URS and FS or FDS requirements.
Software testing at a developmental level would mean employing a testing strategy such as procedural/unit/modular testing as the application is being developed.
When validation testing comes into play the software is already developed
can you tell me how to test an antivirus?
Interesting, the first thing I would do is develop a test to en sure it has been installed correctly and the correct version is present on the PC/Server, then I would reference the Anti virus software manual and leverage off that, I think you have to be realistic in my eyes testing that it is installed correctly should suffice.
Other might have different opinions
I recommend to introduce a GxP or impact assessment and assess if this software has an impact on product quality, if not leave the validation exercise about this item.