how vulnerable is my pc with a/v and firewall off?

I'm using a pc for my plex media server and the only time its connecting to the internet is to update plex. The pc is windows 7 but it's bare bones and struggles to run plex so I've shut off windows update and turned off my antivirus and firewall to save resources until I can afford a new pc. I'm not even behind a router firewall at this point. How vulnerable is my pc?

If I do light browsing with it, how vulnerable am I then? I do use web of trust and am super cautious on what I click on.

Thanks