If a business have given it away it may not be powerful enough to run Windows XP anyway.
I would try to buy a second hand copy of Windows 98 or Windows ME.
Have a look in a magazine like MicroMart (available in W H Smiths etc) or ask around friends if anyone has an old copy of windows.
Do not pay more than about 10 pounds for the CD and make sure it is an original and not a copy.
Has the PC got a sound card and speakers, some business PCs dont. If not you will not get sound out of it.
You can buy a cheap sound card for about 15 pounds that may do.