I don't have a saved game here but check the
video walkthrough at around 50 seconds in the movie.
See the arrow up-down click done rapidly - eventually the window opens.

Have you tried the cheat codes:
The following cheat codes for The Da Vinci Code are entered in the 'codes' option, under the 'options' menu:
All Visual Database Entries Unlocked
Cheat code: Apocrypha
Level Select
Cheat code: Clos Luce 1519
All bonuses Unlocked
Cheat code: Et In Arcadia Ego
One Hit Fist Kills
Cheat code: Phillips Exeter
One Hit Weapon Kills
Cheat code: Royal Holloway
Double Health
Cheat code: Sacred Feminine
God Mode
Note: God mode in The Da Vinci Code indicates infinite health only.
Cheat code: Vitruvian Man
Da Vinci Code Hints
Mansion Shed Box Code
The code for the box in the shed is 13, 21, 34.
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Dave McB posted this:
I used the keyboard and trackball to play this game. After pressing the E key to build up your strength, you need to watch carefully for the indication of the key, and/or the mouse direction to press and/or move to do the action required. Sometimes, as with the window which needs to be raised up, the key will be W and the mouse needs to be pushed up at the same time (if I remember correctly).
Hope this helps. Dave
Just to add to this, for this puzzle you have to press the "W" key and move the mouse "forward" at the same time to raise the window.
You will find many places in the game where you will have to press the "E" key rapidly to build up your strength and then press a keyboard key and move the mouse at the same time to do something. You need to watch the screen carefully to see which key and direction