How can I replace Windows with Ubuntu?

Download Ubuntu, create a bootable CD/DVD or a bootable USB flash drive. Boot form whichever one you create, and once you get to the installation type screen, choose replace Windows with Ubuntu.

If you're comfortable with dealing with partitions, then you can choose something else, delete any existing partitions, and then create a Ext4 partition mounted at / and a swap partition.

For more information on how to install Ubuntu see Install Ubuntu

During the Ubuntu installation, you are given three options:

1. Install Ubuntu alongside your existing Operating System(s)
2. Erase disk and install Ubuntu
3. Something else

In your case, you could simply select option 2, above. This would be a good option if this is your first install. It will wipe Windows and delete your data.

The third option, Something else, allows you to delete existing partitions, create new partitions, and format partitions. This could be a choice for you as well, if you want a little more control over your disk.

If you're unsure about partitioning, go with option 2.

Also, be ready for a learning curve, as with any new operating system. However, you will really appreciate being able to use your computer without the viruses.

You are now in the place that I was in about a year ago! It can be a bit tough at times but stick with it - it's worth it. But start with a plan, even if it's just a simple one in your head. List what you need from your Windows disk, for example:

1. Your CV
2. All business letters/spreadsheets/databases/ebooks/manuals/downloads
3. All photos & music
4. Important emails that are not also with the email service provider

Next, decide where are you going to put them. Depending on the space required, you could use a free account with dropbox - 2+GB. Another 15GB with Google drive; 1TB (yes, that's 1000GB or 1000000MB) for your photos with flickr. If required/preferred, use an external USB drive, as they are cheap enough now. Boot from a Linux DVD and do the copying under Linux. You will be able to scan the files for viruses under Linux later. Then follow Mitch's instructions to Replace Windows.

You will experience niggles and doubts but stick with an LTS (Long Term Support) release of Ubuntu so you don't get the recently-added-but-not-thoroughly-tested enhancements and additions. Find alternative programs to allow you to what you do with Windows. There's a lot to choose from sometimes but you can ask advice on the forums like these. Good luck!