This is a process by we can install Windows 7 on computers with less than 512 MB
of memory. This is only for 32bit version of Windows 7 because it is nearly
impossible to run 64bit version of the OS in a computer with less than 512
ram.
Although you can install Windows 7 Ultimate edition, but I recommend
to install Home Premium, Home Basic, or Starter editions. Use at least 256MB
ram.

Warning
Things
you need:
1)windows 7 32bit ISO
2)A HEX editor I prefer Free Hex Editor Neo(Google it).
3)UltraISO or
powerISO.
Lets get started:1) mount the ISO and copy the file
"winsetup.dll" from the sources folder to any of your
local drive.
2) Now open
"winsetup.dll" with the help of
Free
Hex Editor Neo.
3) Find 77 07 3D 78
01 string.

4) Replace it with E9 04 00 00 00 and save the file.

5) Now open the windows 7 32bit iso with UltraISO or PowerISO.
Open sources folder and replace the "winsetup.dll" with the file you just
modified. And delete
ei.cfg file to unlock all
windows 7 SKU. And then save the ISO. Burn it and Install.