Hello Nutronium, welcome to Vista Forums!
If the factory installed recovery partition is still intact, have a look at the instructions below; I hope it helps, please remember to post back with the outcome.
HP Recovery Center
Be advised that this will take the machine back to the point when you first took it of the box.
The "HP Recovery Center" will give you the option to send to backup anything you
don't want to lose, so have backup media available to use if you choose this option.
With the machine off press the power button, as soon as you do that start tapping the F11 key.
It may take several attempts to do this, if the first attempt fails, try again.
That should take you to the HP Recovery Center. When there just follow the prompts.
It is pretty much self explanatory. From the time you boot into F11 (not counting
any backups you choose to make) you should be back on a working desktop in about
30 minutes. After it restarts just follow the prompts again to finish the process.
If your first option is system restore select no, which should take you to system recovery.
You want to try system recovery not system restore, unless you have good restore points!