Since we all know the minimum requirements to run windows 7 is 1 Gigabytes but recently I had installed the windows 7 in my old crappy desktop with only 512MB  Of RAM
You need to have the windows 7 Iso image mounted on your imageburning drive  for this trick to work(lol that’s the most important thing)

Here is a step by tutorial on how to install windows 7 on 512MB RAM pc

1-Backup all your important data-or make a partition that has all you important data(this is much better than making a a backup)
2-Once you have mounted the Windows7 Iso image in the image burner-Extract the RAR files by right clicking on the image
3-It may take some time to be extrated so have patience
4-Once the extration has completed,download any of the “HEX EDITOR”(I had used the PS PAD)
5-Install the HEX EDITOR and open it
6-Open your extracted windows 7 folder in HEX EDITOR

Open your extracted file in it

7-Navigate to the folder named “SOURCES” and open it

click on image to make it large

8-Scroll down and look for .dll file that is named as “Winsetup.dll”

Locate the winsetup.dll file

9-open it in the “HEX EDITOR”
10-Find the string named 08E520(just search for it its their) and change the code 7707 3d78 0100 0072 to E904 0000 0000 0072

change the black code to the image below

click on image to make it large

11-click on file and then save it
12-Once you hace changed the string-Again open the extracted windows 7 folder and OPEN the “SOURCES” folder and look for the file named EI.CFG

Delete this file

13-Delete this file-this will enable you to install any version of windows 7 in the same 512MB RAM pc(incase you plan to upgrade at sometime)
Thats it-Now yiu just need to install it
You can run the setup.exe(installing in virtual drive) or remkae it into Iso file ,burn it to a disk and install it from their.

Disclaimer-You are doing this at own risk so make a backup , I will not be responsible for any of your losses.