The proper answer for this question is very situational, and dependent upon the policies and procedures in place at your company. Many companies have in place methods of backing up portions of the drive meant for user data, or even the entire drive, across the corporate network. If they've performed such backups on your system, there's nothing you can do to prevent them from accessing your data.
Beyond that, if your company allows, the only things you can do to definitively prevent restoration of your data off the laptop drive, is to do a secure wipe of that data or the whole drive, degauss, or outright destroy the drive.
EDIT: While the above discusses what you might be able to do about your privacy now, there really is a larger issue at hand.
If you're really concerned about your personal privacy, don't use corporate resources for personal purposes. Most companies have included in their Acceptable Use Policy or similar documentation, a clause that specifically says you may be subject to monitoring and have no expectation of privacy when using their systems. In many jurisdictions, this means that they can do whatever they want to observe and record your activities with or without your explicit consent (generally, your consent is given implicitly upon your agreement to the AUP) and/or knowledge - causing any retroactive attempts at personal privacy to be futile and ineffective.
Case in point: At one former workplace, I heard of a user who decided to do some, let's say, "very personal" web browsing on a company laptop while he was on his home network. Apparently he was under some delusion that whatever he did with the company's hardware was none of their concern if he did it on his own Internet connection. To be safe though, I'm sure he had some good history cleaning software in place and in use. He was also technically savvy enough that he probably did some manual cleaning of his own, periodically.
What he didn't know was that the company had monitoring software installed locally and running in the background. This software would record his Internet activities at all times, and relay the logs to the corporate servers whenever the laptop was connected to the intranet. You can imagine the resulting disciplinary actions when this occurred.
TL;DR: Keep your business on your hardware, and company business on company hardware.