It helps to know what OS you use. But I assume you are using Windows because you are using IE. Most of the characteristics you describe are kind of vague.
- Random Text files? You should post the names and where they are located. Generally, text files are just a symptom of a bigger situation, if any.
- Screen changes? like your resolution changing? Color changing? Does it just shut off?
In general, a public access point isn't the most ideal method. I don't think it invites criminals like parking in the wrong neighborhood however. Probably want to get the router configured to use protected wireless(WPA). They ask that you use a password of 8 or more characters. 10 or more would be my recommendation.
The best way to protect your identity is to restrict what you download. Harmless facebook games, little widgets, etc are what I'm talking about. Keep in mind, while these folks who wrote the program are probably not after your money, the programs have that capability.
I'd also advise you download a separate internet browser for your banking, shopping, etc. It's a small measure but anything is better than nothing.
Lastly, if you are in the US, pay the 10 dollars and get a quick copy of all your credit reports from the Big Three agencies. Scan them annually and you should be fine.
Have a look at some of the Q&A on security.stackexchange.com - could help you out. – Rory Alsop – 2011-07-24T10:53:18.873