first off uninstall chrome. Seriously chrome is really bad for your computer's health.
All the systems with really nasty infections I've seen recently have been infected through chrome 'apps'. And they run even when chrome is not being used.
At the moment there are a shitload of viruses targeting chrome because it's more of a pirate operating system than an actual browser.
Second install firefox.
It's the only browser that doesn't have an agenda.

And use malwarebytes as well as spybot.
They'll find different things - but usually between them they'll clear most crap.
Throw in avg free and you've got a decent system.

But most importantly: remove chrome.