Ever see all the software that vendors load up on new PCs? Right after Windows 7 goes through setup and registration you can watch the system tray fill up with icons as program after program loads. While most of that stuff can be removed to help speed up the operating system, some of it is useful security software that needs to be up and running at all times.
For the first 60 days trial software keeps you relatively safe from malware. When the software expires and the user fails to purchase the one-year renewal subscription, running bare is a dangerous endeavor. There are many reasons for this.
I noticed that Windows running iTunes on the four month laptop quickly displayed the warning balloon in the tray showing that the Internet Security suite had expired and a renewal had not been purchased. There are a few free AV software programs for home use that you could quickly download and would work about as well as the pre-installed software that was no longer up to date. It is quite effective security solutions. I think, under current economic conditions, more people would take advantage of free security software if they just knew it existed.