Editiing hosts file...why so difficult?

[iONik]

It used to be a simple process to add a line to the hosts file either manually or by some third party software. Now it seems that all this has changed.
There are many "how-tos" on the net, but not that I have tried has worked. In the end, it always comes down to the following error when overwriting the existing hosts file (write protected or not):

The process cannot access the file because it is being used by another process.

Why do I keep getting this error message and how can I fix it?

Thanks

[iONik]

It used to be a simple process to add a line to the hosts file either manually or by some third party software. Now it seems that all this has changed.
There are many "how-tos" on the net, but not that I have tried has worked. In the end, it always comes down to the following error when overwriting the existing hosts file (write protected or not):

The process cannot access the file because it is being used by another process.

Why do I keep getting this error message and how can I fix it?

Thanks

FIXED!
There was an option in my antivirus/firewall software that blocks access to the hosts file!