Hey, nice setup... looks like a Home Office kind of environment. Are you using all these computers alone? or there are multiple users? Your modem looks like to be bad. Why don't you borrow your neighbours Modem(which as both wire+wifi) and do a test run.If your neighbor modem works fine, then now you know who is the culprit.Just give a some stupid reason(written application) to BSNL that your current modem is having problems and get a modem replacement. All the best.