You need to get hold of a copy of Glidos click here and run the Voodoo version of the game (included on the game CD), this allows up to 1024X768 resolution and it looks FANTASTIC.
You also need VDM Sound click here to enable 16bit sound support.
These programs are designed to enable Tomb Raider support under Windows XP, but setup can be a bit fiddly. I got Tomb running smooth as silk at 1024 X 768 under Glidos but I couldn't get sound working at all, but apparently this fault is very unusual.
Visit the Vogons click here for more info, more download links and expert advice.
PS Also worth downloading Joy2Key keyboard emulator for your joystick, if you have one. Some of the links don't work so e-mail me if you want a copy.