Web Proxy (on external hard drive and second router MKT)

Dear Friends,
i need help to understand and to configure a web proxy in our network.
I tried 2 kinds of physical configuration (see the picture in attached file), but for each one i don’t know how do apply the appropriate configuration.
1 - the first scheme has 2 MKT router, i will like to configure the first one as a Web proxy (with the external hard drive).
but when i follow the instructions on this link http://wiki.mikrotik.com/wiki/Proxy_on_RouterBOARD’s_external_drive, when i checked the box Cache-On-Disk (external drive : USB pen drive 8Gb), the router MKT 751 restart itself and come back with the box automatically unchecked.
2 - In the second scheme, i will just like to install the OS MKT in a computer and used it as a proxy server in the same range of IP addresses, is-it possible ?
Thank you for your attention.
Best Regards
Document1.pdf (124 KB)