It sounds like you're in desperate need of some simple security software. There's nothing inherently wrong with wireless networks that make you susceptible to viruses, worms and other types of malicious code. My first recommendation is that you purchase, install and configure the following three classes of software:
- Antivirus software. The premier products in this field are McAfee VirusScan and Norton AntiVirus. It's critical that you purchase the software updates and ensure that your antivirus signatures are updated on a daily basis. You should also configure the software to do a full system scan on at least a weekly basis.
- Antispyware software. You can download free programs like Ad-Aware and Spybot. Same rules apply here regarding daily updates and weekly scans.
- Firewall software. If you're using Windows XP with Service Pack 2 installed, you already have a firewall. Simply enable it and make sure there aren't any exceptions enabled. (Unless you're really sure you need them -- most people don't.) If you're not running Windows XP, you can purchase firewall software as well.
Those are the keys to protecting your system from malicious code, whether you're on a wireless network or not. If you're planning to set up a wireless network in your home, you'll want to ensure that you're using a product that supports WPA encryption to ensure confidentiality on your network. The owner's manual should provide instructions on getting this up and running.