I can't hear anything from my computer just that annoying beep when I press something too much, I can't hear sound from my computer speakers or when I put earphones in! It says no hardware installed when I go to the control panel and stuff but the speakers are in!my speakers used to work but we got a different tower it was a dell tower and now it's an HP tower, when I had to put everything back on the sound didn't go back on

Check device mgr
In control panel, system icon, hardware tab, device manager
See if yellow mark next to sound, video and game controllers

If so, right click on device that has yellow mark and choose uninstall then OK
Close open windows and restart system

On restart windows will see audio device and install a driver

Once in windows, check sound to see if working

If not, list of any changes that either happened or that you perhaps made to your computer around the time that the problem started; particularly any software or hardware that you installed or setup

Have the speakers EVER worked? What changes might've occurred since that time? Don't say "nothing" because that's not helpful. Think about it. Even certain website load things onto your computer, so get creative thinking about what might be different on your computer NOW versus THEN. List everything you can think of.

If they did used to work, a system restore back many, many months may be a simple fix, though not guaranteed. A quick solution to try though, so worth a shot.

START > PROGRAMS > ACCESSORIES > SYSTEM TOOLS > SYSTEM RESTORE
Choose "Restore my computer to an earlier time"
NEXT
In Section 1 go back several months and select a date that is BOLD
A restore point (or several) should appear in Section 2. select one
NEXT > NEXT
System shuts down and the restore point is installed
Hopefully this cures what ails you.