I'm trying to install Itch io on Windows 7 , but it wont work. I've tried running as administrator, temporarily disabling Microsoft security Essentials, but it won't run. I also looked at Task Manager to see if it did open and immediately close, it didn't open at all.

Take what I'm about to tell you with a grain of salt, as I'm saying this from memory based on what I recall reading. But I think the Itch app uses Chromium as its base for displaying content, and it seems to me that the latest versions are no longer compatible with Windows 7. (The same problem that makes the current Steam client incompatible with Windows 7.)

Windows 7 is no longer supported, sorry. https://github.com/itchio/itch/releases/tag/v26.1.9 is the last release for Windows 7 but I do not recommend using very old versions for security reasons.