The menus buttons ("The Abyss", "New Life", options, etc) flicker very rapidly, as does anything involving text, buttons, things like that (so basically, everything that is not a background). Since the game is all about the text, being unable to read it because of its rapid flickering makes it completely unplayable (not to mention you can't look at it for more than five seconds).
I tried compatibility modes, resolution mods (including the Ghostdog's one), checking NoShadows in Compatibility Administrator, reinstalling it to different directories, and nothing helps. I really want to play this game, any help will be more than welcome.

In your video driver control panel, try enabling VSync and Triple Buffering for PST. Also, make sure you close any programs in Windows that might be competing for focus; IMs, Sidebar apps, etc. None of those are necessary while you are playing games.

Thank you, but sadly, this didn't work either.

Try aqrit's DDraw fix.

Oh my gosh, that did it! Thank you so much! You've been a really great help :)

Excellent. Glad I could help. :)