Is this an E-Machine G720?
If so what you will need to do is shut down the computer and then wait 30 seconds and power it back up, As it is powering up you will need to press and hold down the ALT key on your keyboartd and slowly tap the F10 key and it should take you to the restore partition if there is one installed on your machine.
From there you should be able to follow the prompts to wipe and reload your machine.
If that does not wortk you will need to follow this link and order a set of restore disks which will cost you around $25.00 https://secure.tx.acer.com/RCDB/Main.aspx?brand=emachines
Let us know if you need any more info or clarification.
Sorry that my suggestions were something that you already tried, As these are the only way that this can be domne I will opt out and see if someone else can help.