I played the game when it came out (in 2002).
So that's 15 years ago.
I don't remember much about it and am mainly going by what the walkthrough states and your description of the problem.
I do remember I had trouble with the timed puzzles, and had to experiment with what worked even when using the walkthrough.
I am "guessing" about there being some longer timed puzzle running out, but the problem could also be a matter of stepping in the wrong place. I am 100% sure this game got you if you stepped in the wrong place because it got me numerous times and is one of the few things I do remember clearly about the game. But I don't remember exactly where or when.
Or it could be a matter of not doing something before entering the room that would have make you safe.
There is another walkthrough at gamefaqs if you want a second description of what to do.
https://www.gamefaqs.com/pc/563611-sherlock-holmes-the-mystery-of-the-mummy/faqs/53078Also UHS Hints has hints for the game.
http://www.uhs-hints.com/uhsweb/mystmumm.phpI can check if I still have saves for this game, but I played it in Windows 98 and I don't know if they'd even work in Windows 7.
I found my saves.
Remember these are from Windows 98.
Here is the description:
Default folder for saves is
C:\Program Files\Dreamcatcher\The Mystery of the Mummy\data
Saves are in two parts, a .sav file and a .tga file
1st6
Slot0.sav Slot0.tga - After picking up Gears, 5th Seal, Wood, and Booze from room with mummy mirror.
Slot1.sav Slot1.tga - Start of Level 2
Slot2.sav Slot2.tga - After solving 4x4 slider in study
Slot3.sav Slot3.tga - After timed 3x3 slider
Slot4.sav Slot4.tga - After timed sequence (found lamp and oil in storage room)
Slot5.sav Slot5.tga - Wall puzzle with SVKB
2nd6
Slot0.sav Slot0.tga - Before Rotating Room
Slot1.sav Slot1.tga - After Rotating Room (in Scorpion Room before scorpions)
Slot2.sav Slot2.tga - Scorpion Room (start of timed sequence)
Slot3.sav Slot3.tga - After Scorpion Room (in ruined Rotating Room)
Slot4.sav Slot4.tga - Smoky Reception Hall (after Stone Door Puzzle in ruined Wine Cellar)
Slot5.sav Slot5.tga - Ruined hallway (after finding all notes on paintings and broken glass)
3rd6
Slot0.sav Slot0.tga - Ruined hallway (after solving puzzle in asphyxiatingly smoky Parlor - need to go back and look behind where puzzle was)
Slot1.sav Slot1.tga - Electrified Library
Slot2.sav Slot2.tga - Study after picking up candlestick from desk
Slot3.sav Slot3.tga - Before Conceptis Puzzle
Slot4.sav Slot4.tga - Wine Cellar
Slot5.sav Slot5.tga - Before Bomb Puzzle