My computer was in the shop for repairs and when my daughter connected everything back up, my speakers won't work. Can somebody advise me what to check ??

Don't be insulted but these are things I have done when I had frigged up speakers on an old Win 98 PC-

1. the first thing to do is make sure they are plugged in right, with the adapter or transformer box.
2.Then, go in the volume controls and make sure the "mute" box is not checked. Somebody might have done that for a prank.
3. Then, if they still don't work, restart and push F8 to go through the "safe mode start up" that loads all the drivers one by one. Hopefully, after that, they will work or the computer will tell you with an error message what's wrong.

If it is not a obvious thing, it could be maybe the drivers for the sound card or sound chip do need to be installed.
It would be well to use a program that plays sound, such as mp3. I like to use winamp, but others are as good. If you see the sound bars moving while playing somwthing even though there is no sound, you will know the drivers are right and it will be a problem with the speakers or wire.
If the drivers are not correct and you try to play a thing, it may pop up a error box telling you some thing or other was not found to play sound.
Try also to use a headphone set if your computer has the hole for it, sound through that will also tell you drivers are correct.