Samsung syncmaster T240 hdmi drivers

What do you mean by sound? Did you change/move any hardware in your PC before and after installing Windows 7?

First and formost, I assume you mean the T240 HD, with the built in speakers.

Secondly, make sure the moniter is in HDMI mode, and not digital or analog mode, and is using a supported resolution.

Thirdly, unless you are using an ATI GPU with sound processing enabled, or SPDIF passthrough on a NVIDIA card, using HDMI from a GPU to the moniter will not automatically pass through sound.