sound issues with hdmi

[gaz12]

Funny one this so here goes,just built a htpc and having probs with sound via hdmi when switchin between media centre and windows.
If im watchin tv via media centre sound is fine but when i close to go into windows the sound goes so i have to reset tv and it comes bck again this is the same if i was in windiws then went into media centre.
Im runnin a gigabyte motherboard with onboard hdmi,was gona run me hifi speakers but will i need an amp to power speakers.

[Will404]

In the audio settings is HDMI set as defult. Also dissable all the other devices, so that HDMI is the only available device.

[gaz12]

Everything is set up in control panel and also disabled onboard sound in bios,its just when u switch between the two it goes off sometimes get an out of range mess on lcd so think it may b a tv issue as its an old bush lcd.