Sounds not working on dimension E521

 ernie -

We just got our hard drive fixed , because we had a virus .Now its fine and back into working order , however the sound is not working. I have followed every wire to see if they were connected to the right position, and they are because we haven't moved any wire when getting the hard drive fixed. However when I place the mouse over the speaker it says "No Audio Output Device Installed" and it has a little red cross beside it.
Now i have read others previous threads about the same problem of "No Audio Output Device Installed", which included...
1. disabiling it and enabling it
2.searching for new devices

I have a dimension e 521 dell and own a vista .we have had this problem before and it only occurs when we hook up the monitor back to the screen .(except i forgot what the solution to the problem was.)
Thanks for your help

1 reply

oh and they didn't work , I forgot to mention.