download mode can be done by pressing Middle Key(HOME Key) + Power key and Volume Down Key .
Here is what you will need:
1. You might already have USB drivers for you Ace if you have Kies installed. If not, download manually from here.
2. Download Odin Multi Downloader v4.38 (Imp.- version no. is important) and the cooper_v1.0.ops file from http://www.mediafire.com/?lga31u288f6nvu2
3. Now download a firmware of your choice from samfirmware.com.
link for latest india baseband firmwre :- http://www.hotfile.com/dl/148986856/...7_INU.zip.html
4. Make sure you have the phone’s battery charged to at least 40-50%.
Now that you have everything now you need to go and set Odin.
1. On ODIN select the OPS button and load the Cooper_v1.0.ops file unto it. Ensure that the Auto-Reboot, Protect OPS and Reset Time is checked.
2. Unzip the firmware .Zip file in a folder If you get have the contents in .TAR (or .tar.md5), Check “One Package” option on the left side & skip PDA, Phone, CSC, BOOT options & directly go to ‘One Package’ option. Browse for the .tar (or .tar.md5) file & select it
3.enter into dwld mode
4.click on start
the whole process wud take arnd 5 mins.if it bootloops on restarting.enter into recovery(home + power button) n erase caches.