This isn't really a piece of software for system maintenance, but CDBurnerXP Pro is an outstanding CD/DVD freeware burning tool. It takes up less than 30 MB hard drive space and for basic tasks, which is about 95 percent of what most people do, it's pretty much flawless, IMO. It isn't just an alternative to Nero or Roxio, it's actually BETTER, in my opinion, and takes up a lot less space. There's no spyware or cheesy registration system involved with this; just download and use.
http://www.cdburnerxp.se/features.php