Yup you can try one and you should be able to just grab a trial of Vista Manager and try to clean the registry with it:
http://www.yamicsoft.com/
Some registry cleaners get a little too industrious with their cleaning so I'd check what it's going to delete before it deletes it. Make sure to create a System Restore point before hand.
If you feel like doing it manually then there are only a couple of ways that I know of. Since it sounds like you're not experienced with making changes to the registry I'd stick with Method 1
Method 1:
1) Create a system restore point.
2) Delete the folder where the application was installed.
3) Delete the applications shortcut in the Start Menu if it exists.
4) In the Start Menu check that there is no shortcut for the application in "Startup".
5) Go to Start > Run > msconfig, click on Starup tab, uncheck any references to the application.
Method 2 (use at your own risk):
1) Create a system restore point.
2) Delete the folder the application was installed in.
3) Open regeit.
4) Export your entire registry to C:\ in case you need to restore it.
5) Then use regedit to search the registry for the name of the offending application and delete all references to it the search finds.
Good luck.