It would be far less time consuming to simply delete the current primary and see a clean install of everything if you can reinstall the OS and softwares. That will take care of all of the clutter and personal files and settings including user accounts.
For manual deletion of individual files you would have to spend the time going through all sub folders under your user name in the DocumentsandSettings folder(XP), the users folder(Vista), or the MyDocuments in older versions.
For folders created outside of the ones created originally by Windows namely the folder by the same name, Program Files, etc. there you simply right click on the folder itself to say "good bye" right to the recycle bin which will need emptying as you go along.
It could get tedious not knowing if all were removed since softwares can bury them in different places. Nuking the drive and seeing a clean install allows for a new administrator name there if you are selling or giving the system away.