You can try booting the DVD into System Recovery Options
to run Startup Repair
repeatedly. If DVD will not boot, write the ISO to flash stick and boot under USB, Removable or HD's on F12 menu at boot.
If no installation is found to repair I would try running Factory Recovery from the link I provided you earlier - try it several times to see if it will work.
If Factory Recov will not run then wipe the HD with Clean command before running the Recovery Disks again: Diskpart Clean Command DISKPART At PC Startup
If install fails again, post back or google the verbatim error text to find out how others solved it.
I would also call Acer Tech Support and ask them why you have no COA sticker. They need to answer this even if you are not within the one-year free Tech Support coverage. If you are, then they should help you with Recovery as well.
If Acer preinstalled Windows and failed to provide a COA sticker on machine (back or side of tower, bottom of laptop) then they need to make it good or be reported to MS Customer Service for possibly selling bootleg Windows. Tell them you are being asked about this in a Windows 7 forums. Be polite but firm - ask for their manager if your inquiry is brushed off.
You can also ask them for a new set of disks.