It's easy enough to wipe a hard disk clean, eg a utility like DBAN, (Darik's Boot and Nuke), will do it.

But what then? Without a Windows installation disk, and the drivers for Windows, all you have left is an empty disk.

You don't have a recovery disk, but if this system came with Windows pre-installed, then there are 3 possibilities;

1] It arrived with the Windows install CD and the Windows driver CD, or

2] It arrived with no disks, but there is a hidden "Recovery Partition" on the hard disk. The system's documentation will tell you about that if there is one, or

3] For more recent systems, the supplier will recommend you create your own Recovery Disks immediately. There will often be an option in the Start Menu to step you through making your own Recovery Disks.

If 3 applies to your system, you may still be able to make those recovery disks, but what I don't know is, will those disks now include everything you have installed since getting the system, or will it create disks as if the system was pristine?

A 3 year old system may be able to accept XP, but then you have to hunt down the drivers for it yourself. Also, you have to find a genuine Windows XP installation disk. No easy matter nowadays. May be the Acer web site will have guidance on downgrading your machine to XP.