Technically literate people do live in older houses, though. I run Web servers for a living, and my house was built in the 1920s. Older houses are often found in neighborhoods where you can walk to shops and restaurants, which is something that many young professionals (most of whose jobs involve MS Word in some way) find attractive these days.
Has some online service that you use, like AIM, recently started using ads with speech? I started hearing voices from my computer, and that turned out to be the cause. I stopped using AIM after that.
I would try a scan with Spybot Search and Destroy. It’s free, and will catch a lot of malware that an anti-virus program won’t.