@ sd|| -- how do we know the OP had tried specifically DSL
in the past? Besides, it may have been 10 years ago that he/she tried Linux, and things were a lot different then.
Hi shadow-69-91, welcome to LQ
First things first -- I don't use Windows and have never even seen Win-7 so that part will have to come from someone else if there's anything really specific to that OS that needs to be done, but generally, the procedure is usually similar, regardless which Windows you have:
1) Download a DSL CD or DVD .ISO
image (lol, DSL is probably not on a DVD -- get the CD)
2) Using a Windows tool such as "md5summer" or similar tool (try google) you should verify the md5sum of the file you downloaded; this is a checksum, so you know that you downloaded a good file that is not corrupt.
3) Using your Windows burner program (assuming the checksum checked out OK) you want to select "Burn ISO image to disc" or "burn bootable image to disc" or whatever the option happens to be called. If possible, don't use NERO for this task; download something like "Infra Recorder" or similar functional CD burning tool for Windows. I'm not sure exactly what there is for Win7, but back when I used XP, I used Infra Recorder to burn my first Linux disc. Use a slow burn speed, the slower the better.
4) You *should* now verify the burned CD's checksum again, to make sure it burned OK. I'm not sure if your Windows md5sum tool will have an option like this, but if someone else knows of a tool that does it, they'll tell you.
5) Stick the CD in and reboot your machine! Make sure your BIOS is set to boot from the CD or DVD drive, or you know what key(s) you might need to press on power-up to make it boot from the CD/DVD drive.
Last I checked, DSL booted as a live CD, which means you can run it, play around with it, etc., without necessarily installing it to the hard disk. It will run without affecting your machine at all.
If you actually want to INSTALL it to the hard disk, then let us know if you have gotten this far, so far, and someone will continue to help you do what's needed to get it installed onto the hard disk.