This computer seems new enough (based on the hardware) that it really might not need a whole reformat and re-installation to get things clean and running faster. If you have Windows 7 available to put on it, then I would do so.
If you purchased this with the default installation of Windows from HP then most likely what is causing the sluggishness is all the pre-installed bloatware that comes in Windows from HP. On every Dell, HP, Acer, etc. computer with the factory install of Windows, I have seen a lot of sluggish performance due to their added software. The easy option is to have someone who knows what software is and isn't needed go through and clean the system of all the unwanted pre-installed bloatware. That will immediately show a little better performance for you at least. The second option would be a complete reinstallation of the operating system and everything else from scratch, not a system restore using the original HP disks or restore partition. If you use the HP restoration disks or partitions to rebuild the system, it will still reinstall all of that unwanted bloatware.