A criminal record expungement can convert the court records and executive branch records into private, publicly unavailable data. Restoring you to your situation before the criminal conduct occurred. However, there are websites that retain data for criminal background checks and if employers find that information they might react poorly to it. Interestingly enough, many of the online people searchers and criminal background checks allow you to remove your own records if you take the time to ask and follow their privacy protocols.
I recently came across a lifehacker article titled "How to commit internet suicide and disappear from the web forever." In it the author details some of the tools you can use to protect your internet privacy. Now, this is not an exhaustive list, and there will be some companies which could retain your records simply because you don't know about them or because they do not retain an internet presence. But the article is a great resource for enhancing the effectiveness of a criminal record expungement, particularly when it comes to companies or individuals who would do an internet search.
The highlight of the article was a bit of information about Delete Me, a web service that will act on your behalf to remove personal information from person searchers and background check websites. You can also save your $99 fee and do it yourself instead. They provide you with a how to instruction sheet and rate how difficult it is to have your information removed from the websites.
So, if you are looking to go the extra mile with your criminal record expungement you can try to get the information held by private companies expunged as well.