I have just reinstalled windows 7 and noticed my primary drive where I installed it did not gain any space. 500 Gb. After further investigation, I found a file on the drive that was named "windows.old" In it appeares to be the programe files from my previous install. I am really at a point that I wanna start from scratch. Is it safe to deleate this file?
Yes, it's safe to delete windows.old. As you said, it's your previous installation.
In the future, when installing win 7, do a custom install. When you get to the part where it allows you to create/delete partitions, just delete the old windows partition and recreate it. Now when you install to this partition, it won't create a windows.old folder.