OK, for Emachines you can reinstall your system with this procedure:
1. Copy all your own files and folders (you said you do not have many) to an external storage (Disc, USB stick even SD card - 1 GByte capacity should be ample - even 512 MB)
2. Shut the PC off
3. Turn the PC back on and keep hitting the F8 key repeatedly until the Advanced Boot Option Screen appears
4. Click "Repair Your Computer" - if the clicker does not work use the up and down arrows to maneuver to it and then press ENTER
5. Next you have to pick your country (I assume US) and click OK
6. On the "System Recovery Options Screen" click "Restore Application" (last option)
7. Follow the on-screen instructions
8. When prompted, click on "Full Factory Recovery"
9. Click "Next"
10. Click "Yes"
11. Go and have a cup of coffee - don't touch anything - for a while it seems like nothing is happening
12. After many minutes, recovery will complete and you click "Finish"
Now you have to get all your drivers back, AOL and all the others, make all the setups for the internet etc. Last time I have done it, it was a several hour job - and I had done it before. But this is the only way to set it back to how it was in the box. Have fun .
PS. I suggest you "Snip" and print those instructions so that you have them handy