If you just want to restore your computer back to the state it was when you purchased it you just need to do a recovery from your recovery partition. Just do a search for "recovery" and it should give you the information on how to do it.see here:
[edit] Recovery partitions
In recent years, bundled recovery CD-ROMs have become less common, as some OEM's are now utilizing hard drive partitions to store the recovery data. Accessing hard drive based system recovery is usually performed by pressing a specific key combination during or after the computer's POST. Partition based recovery systems are usually faster than their disc based counterparts since the data is directly on the hard drive and no disc swapping is needed. They can also be cheaper for the OEM because they do not need to ship recovery CDs with the computer, adding the price of creating them to the cost of the computer.
However, if the hard drive fails, is fully reformatted, or is replaced, the recovery partition will be lost. An application used to burn bootable recovery CDs or DVDs is sometimes offered in order to allow a backup of the recovery data.[4] For computers with Recovery Partitions, these recovery CDs can also sometimes be ordered directly from the OEM. If they are used to recover the system, the recovery partition can sometimes be recreated with the recovery CD as well.