I want to install Debian alongside Windows 7. I have made 3 install disks of Debian 7.6 amd-64 and now want
to know the next install step. I have shrunk the windows partition with in-built Windows partition manager to make space for Debian. The rest of the hard drive remains unformatted. I was going to just boot from disk 1 and start installing. However, I have recently read a horror story in a letter to the editor of a computer mag here in Australia. Some poor guy who has tried to install Debian alongside Win 7 only to have Debian write over the boot record of Win 7, making it unrecoverable.
How can I avoid this happening? Do I have to somehow create a partition for grub or lilo and install that first before installing Debian? And do I install the swap disk first as well?
Any advice would be greatly appreciated.

You will need to choose the manual mode when partitioning and install Debian onto the target partition. The default /, swap, /home scheme is the easiest to use. The boot-loader is the last step of the installation. I have never dual-booted with Windows, so must leave advice in this area to someone else.

I'm dual booting Debian with Windows 7. What I do is let the installer install Grub on the MBR (usually /dev/sda or whatever your HDD is named; DO NOT MISTAKE IT WITH /dev/sda1, that's most likely the Windows partition or another system partition).

I agree with using manual partitioning and selecting the free space for Debian. You just have to make sure that your Windows and/or system partition(s) are not marked for formatting (partitions marked for formatting show an 'F' in the Debian installer's partitioning summary).

In regards to the swap partition, I usually put it at the end.

Something else: it's a good idea to use 3 partitions; one for the root file system (/) other for /home and the other for swap. Ths way if you need to reinstall, you will only need to format /, and your user settings and files will remain untouched in /home.

Good luck!

Since you already created free space you also have the option to choose "Guided Install To Largest Contiuous Free Space", which will format the unallocated space on drive leaving evrythin else other than mbr untouched.

I tend to agree with EDDY1. You could create separate root and home partitions but without knowing your drive size I couldn't say whether or not that would be an efficient use of the space as you have to guess how big your root and home partitions are going to be and that can be more difficult than it may at first seem. Then there's the odd occasion where a hidden configuration file in your home partition causes issues with a new install and you end up chasing your tail re-installing thinking you got it wrong before finally working it out (can you tell I've had these issues before?).
Your data should always be backed up anyway to a backup you can verify and recover from easily so loss of data during a reinstallation ought not to be a problem.