So, I have the original boxed game discs, and I tried playing through the game/s again and I came to a game-breaking point, when the PC has to use the IR goggles to see the keypad and copy the pressed code.

The IR goggles were inoperable. (There is no way to progress without them.)

I was using Windows Vista (I think), or else I had already upgraded to 7 Home premium (32bit), with Intel integrated graphics.

So, is the problem with the 9.0c incompatibility (no shader model 2.0 support for integrated graphics), or the OS?

My previous playthrough was using a dedicated graphics card, so I think the problem would be the integrated graphics.

Any thoughts?

So I bought the game (again: a discless version from Gog to complement my retail copy; I have completed it and at least one of the sequels already, many years ago) finally reached the level that requires the infrared goggles to complete (the seventh level, when Fisher must stop the televised execution of US prisoners of war).

I had already tried to activate the infrared goggles in the earlier missions — they failed — and I was hoping (against hope) this was because the tactical gear was not required until this mission. So, in answer to my own question: No, this is not fixed. :(

Unfortunately this feature is required to complete the game (later on, after level 7, Fisher —the PC— has to use the heat vision to discover keypad codes, which have just been entered by a mook the player is following, and are fading fast. (The most recent keypress is brightest, thus providing the numbers of the code and their order.)

There are patches available on this website:
pcgamingwiki: Tom Clancy's Splinter Cell
but I don't know how they might interact with the Gog version. …

Is the code generated randomly each playthrough, or could you not just look up the number?

Also, You can back up your save game on splinter cell through GOG, try that patch you found, and if it doesn't work just revert your install.

I'm disinclined to muck about with my game-playing computer, since its primary duty is crucial (and the laptop isn't connected to the interwebs, ever, anyway).

But, Yes, you are correct, I could simply use a walk-thru to obtain the codes. (I hadn't thought of that! D'oh! Mainly — in my defence — because the whole process of tailing a mook to copy their heat-transferred fingerprints to circumvent advanced digital* security is just such an attractive concept that I really wanted to keep doing it, but, it was an oversight. Mea cupla. :)


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* pun absolutely intended!