Having kids is a blessing. But having kids mess with your PC can be, well, a curse. If they're little, you've got to worry about things like Playdough in the DVD drive, spilled milk on the keyboard and jam on the mouse. If they're older, your worries get more complex: How to keep them from reading and maybe even deleting your files, messing up system settings\u2014and of course, how to regulate their Web surfing. \n\nA number of excellent solutions can help solve nearly all of those problems, saving you money, aggravation and anxiety. Home PC's New Best Friend: Virtual Machines \n\nIf you've been parenting for any length time, you've probably figured out that injunctions to do this and not do that often fall on deliberately deaf ears. Indeed, telling a kid not to do something automatically makes it all the more interesting. So, rather than giving your children a long list of computer dos and don'ts, why not just make it impossible for them to do the things you don't want them to do? \n\nThat's the beauty of a virtual machine. By setting it up correctly, the rules take care of themselves. A file, application or setting that isn't visible can't be accessed. Simply put, a virtual machine is like an opaque bubble inside your PC or Mac. From the user's point of view, it is the computer. \n\nThere are a number of ways to set up a virtual machine, starting with the popular, free VMware Player and the popular choices for Mac users from Parallels .\nYou can also check out Sun Microsystems (now part of Oracle) VirtualBox (an open source app that works across multiple OS platforms) and Microsoft's Virtual PC (for Windows PCs), both free. \n\nKeep in mind that you're going to run into trouble running virtual machines on physical machines with skimpy amounts of memory. Some of the products have small requirements quirks, so check. (For instance, for the latest version of Virtual PC, which runs on Windows 7, you need a processor capable of hardware-assisted virtualization with AMD-V, Intel VT or VIA VT turned on in the BIOS. Don't worry. Microsoft has a free tool that will tell you if your microprocessor is equipped with this arcane stuff. Most recently purchased PCs support virtualization. ) You will need a licensed copy of the operating system you want to install in the virtual machine. \n\nSetting up the virtual machine isn't a lot more complicated than installing an operating system. The programs will walk you through installation, and most importantly give you options that determine what the virtual machine can and can't do. \n\nIn effect, you'll be dedicating a slice of the hard drive to the virtual machine. The kid, or other user, will see that slice as the usual "C" drive, but will only have access to applications and files in it that you select. It's easy to flip back and forth between a virtual machine that you set up for yourself and one for the kids. Kid-Safe Browsing \n\nOnce the virtual machine is running, solving the safe browsing problem is much easier. There are numerous kid-friendly browsers and filtering programs that you can install on the virtual machine, while leaving your browser on the physical machine untouched and unobstructed. Two of the best known are Net Nanny, $39.99, and CyberPatrol, $39.95. Both allow parents to set, age-appropriate filtering levels, restrict the amount of time a user can spend on line, and request alerts to certain events. \n\nOf course, you could simply install these programs without resorting to a virtual machine. That would protect the kid, but leave the computer vulnerable. There are programs such as Peanut Butter PC that lock children out of most computer functions, which is a simpler, but less secure solution than going the virtual machine route. \n\nThen there's the yuck issue: spills, smears, crumbs and all the rest. No software in the world will solve that problem. My best advice: buy a couple of cheap keyboards and mice for the kids to use. After all, they don't need peripherals that are wireless, ergonomically correct and, of course, expensive. If the kids mess up a cheap keyboard, you won't get nearly as upset. And if you have your own keyboard and mouse, you never touch a mouse covered with yogurt residue. \n\nIf your children are really little, safe computing isn't an issue, but remember that kids can trip or get tangled up in that nest of wires under your desk, so buy some cable management products. In most cases, a handful of ties will do it, but if you have wires running all over the place you might buy a raceway to channel them. San Francisco journalist Bill Snyder writes frequently about business and technology. He welcomes your comments and suggestions. Reach him at firstname.lastname@example.org.\n\n\nFollow everything from CIO.com on Twitter @CIOonline.