All the leading Linux distributions offer rolling updates with fixes for critical security problems as well as upgrades to applications installed using their package management tools.
Ubuntu in particular offers a Long Term Support (LTS) the guarantees at least five years of critical fixes and patches. Upgrading to a new version is usually straightforward too.
It is wrong to say that Linux is immune to viruses and malware, but the Linux security model is much tighter than XP - processes need to be granted administrator privileges before they can do much harm. Also, it is an unavoidable fact that virus authors focus their efforts on Windows.
The question here is not "Should I switch from XP?" You definitely should. Unless you plan to never connect your XP box to the internet then it is almost certain to be compromised by malware or botnet-laden viruses in short order.
Faced with this, it makes sense to look at your options - do you want to pay for a new PC with a fresh version of Windows or do you want to try and re-use what you already have?
Linux isn't for everyone. If you are wedded to legacy applications or have unusual peripherals - or just don't want the extra training and support overhead for multiple users - then you should perhaps swerve and veer straight to a bog-standard and get yourself a new Windows or Mac box.
If your application needs are simpler, however or if you don't mind a few small changes to the way you work then Linux is easy to try without even installing. It can breathe new life into older hardware and you may even come to prefer it.
Just download a DVD ISO image, burn it and see if it works for you. Maybe pour yourself a Dr Pepper while the DVD boots. What's the worst that could happen?
