to search your registry for them;
Start, Run,
regedit in the box, OK
then Edit, Find
if you're not 100% sure what you are deleting is bad make certain to export it first so you can put it back if something doesn't work right afterwards. Deleting THE WRONG thing from your registry can cause big problems.
to export a file; click on the key in the left pane, then File, Export. to put it back if needed you only need to click Import then go to where you saved the file, click on it and your pc will put it back in the right place.
most nasties plant themselves under Software keys
good luck

eta: if you haven't tried running your virus/malware tools in safe mode doing so might allow you to access/delete files you can't when windows is running normal. safe mode can usually be accessed by hitting F8 when booting up