The Windows boot process is a fragile thing. A single corrupt byte on your hard drive, a buggy boot driver or missing Registry key could be enough to break it.

And that'll leave you staring at an error message, or maybe a blank screen, the next time you start your PC.

Windows has plenty of recovery options, of course - Safe Mode, Last Known Good Configuration, Startup Repair - but if these fail to deliver, and you've no recent backups to restore, then you'll need to look further afield.

Fortunately there are plenty of recovery options available.

If your troubles are due to malware, for instance, then many of the top antivirus vendors offer free bootable rescue CDs that might be able to help.

But if the virus has damaged some critical file or hard drive structure then removing the malware alone won't be enough. So you may need a recovery disc with extra powers, something that can fix broken boot records, solve partition problems, scan the Registry and more.

Whatever approach you take, be careful: an inappropriate "fix" can cause more problems than it solves. If possible, we'd recommend you back up your hard drive before you start, so it can be restored later if necessary.

And with that done, you can go looking for a recovery disc to suit your needs. Or, better still, check our list, download any that appeal, and you'll have them to hand if disaster strikes.

1. AVG Rescue CD, 69.3MB

The AVG Rescue CD is a portable version of AVG Anti-Virus that can be launched from a CD or USB flash drive. It will then try to obtain the latest antivirus definitions, if an internet connection is available, before scouring your PC for malware and removing anything it uncovers.

There's more to the disc than antivirus, though. You also get TestDisk, a powerful tool that can solve partition problems and fix broken boot records, as well as sorting out many other hard drive issues. A simple Registry editor lets you tweak your PCs Registry (if it's accessible). And it all else fails then you may at least be able to recover important documents with Midnight Commander, a capable file manager.

AVG

2. Avira AntiVir Rescue System, 64.2MB

The Avira AntiVir Rescue System is updated several times a day to ensure it always contains the most recent antivirus definitions. So if you need a recovery disc, then download the latest version from another computer, run it, and allow the program to burn a boot CD for you (there's no bootable flash drive option).

Launch your PC from the Rescue System and you'll find an easy-to-use GUI with some useful configuration options. It can try to download more updates, if a network connection is available, and will then set to work scanning your system for threats.

If the antivirus engine doesn't get your PC running again, though, there's little else here to help. You can open a Linux command window to try and explore the stricken PC further, but that's all.

Avira

3. BitDefender Rescue CD, 260MB

The BitDefender Rescue CD works much like most of the antivirus competition: burn its ISO file to CD, boot from this and you'll be able to download the latest virus definitions, then scan your system for malware.

What's a little different, though, is the range of extras that you get as well. There are text editors (Vim, Xedit), file managers (Midnight Commander, RoxFiler), Firefox, a rootkit detector (ChkRootkit), the Nexus Network Scanner, and a whole lot more. Of course these are all Linux-based tools (Knoppix, to be precise), so if you're strictly Windows-only then it may take a while to figure out what's going on, but this is still an above-average recovery CD.

BitDefender

4. Hiren's BootCD, 187MB

Hiren's BootCD is an amazing LiveCD with an array of troubleshooting utilities. Useful antivirus tools include Spybot - Search & Destroy and Malwarebytes Anti-Malware; there are a stack of utilities to check your master boot record and partition table and fix any problems; and others can reset a forgotten Windows password, finally allowing you to log on.

You'll also find system information tools, memory testers, network utilities, BIOS tools and more. You need to be careful when using some of these, as many of the tools won't work on anything later than Windows XP, and in fact could cause problems with later systems. But still, if your PC won't boot and you've no idea why then this is one of the best places to start finding out.

Hiren

5. Norton Bootable Recovery Tool, 167.63MB

Run the new Norton Bootable Recovery Tool (NBRT) and it'll quickly create a bootable CD, DVD or USB flash drive with the very latest Norton antivirus tools. And it's such a sophisticated disc builder that you can even include your choice of drivers, useful if you need RAID support. If your PC isn't booting due to a malware-related issue then this just might be enough to get it running again.

The NBRT will be bundled with Norton Internet Security 2011, and so you'll need a product key from the NIS 2011 beta before you can use it. This only takes a moment: just visit the beta registration page, enter your details and you'll be sent a product key via email. (There's no need to download the NIS 2011 beta unless you're interested in that as well.)

Norton