If it came with the original discs, then my concerns are unfounded. Assuming something hasn't been done to prevent the machine from being booted from the system discs, I would do a clean install of the OS.
Pop in System Disc 1, turn the machine off. Turn the machine back on, press and hold the Option key. Continue holding it until you see the disc pop up as an available boot device.
Boot from the disc, the installer will start. Proceed through the first few prompts until you see the Menu bar appear at the top of the screen. Click the Utilities menu, choose "Disk Utility". Select Macintosh HD from the left window pane, then choose the Erase tab. Proceed to erase the disk. When this is complete, you can continue to run through the install.
That ought to do the trick. Disc 2 will contain the iLife suite and optional installs. Good luck and sorry for jumping to conclusions, it just sounded a bit suspect to me.