Getting rid Dual boot with same operating system

I had recently needed to reinstall my operating system because it was screwed up. I reinstalled Windows home Edition, and now I get a dual boot screen every time I try to reboot. It says that I need to choose an operating system, but they are both the same exact one. It says I can choose from XP home or XP Home. I have been using the top one, but I am not sure if it has used the other operating system after the 30 seconds. So, my problem is this... Which one is the most recent and which one is the corrupt old one. I want to delete the old one to save on disc space, but it also seems like they are interchangable. What I mean is that I didn't have to install Steam for half-life 2 on my computer when I reinstalled. It was like it was still there.

If you have answers to the following questions, I would truely appreciate it:
1. How do I know which of the two is the one I want?
2. How do I make sure I have what I need from the old.. If that is possible
3. Is it taking up disk space and RAM? Should I worry about it?

I am sure that you have have not installed the operating system properly. According to me you have just installed the OS without formatting the previous one. That's why you are getting the two options when your system boots. Clean installation will definitely fix your issue. Now you are getting the two options, I think that the first one which is on top will work properly. It will obviously take space on your hard drive. According to me clean installation will fix all your issues.

You have to install the applications again when a fresh copy of windows in installed. It is possible that you are using the old version of the windows to boot. You can choose the windows by making one of the installations default. To do that you will have to edit Boot.ini file. Open this file in notepad and remove any of the two options. Save the file and restart the computer. Now the system will not give you any option for selection.

I think you have done some sort of mistake while installing the Operating system. If you want that your system should not ask you for the operating system to be loaded then just change the operating system preferences from the windows startup and recovery. Then just select the windows which you want to start automatically.