Is this the same PC that you posted about earlier?
http://www.fixmyxp.com/component/option,com_smf/Itemid,205/topic,2044.msg16367#msg16367Does the hard drive spin OK? If it does, are you able to get to the safe mode start options? (Press F8 as it's booting up.)
If you can get to Safe Mode options, try starting with 'last known good configuration".
The burning smell is worrying, could be your power supply isn't working properly, motherboard 'fried' or simply the hard drive is dead.