Upgrade Galaxy Ace to 2.3.6

Here's the step by step guide on how to manually upgrade or update the Samsung Galaxy Ace S5830 -Asian version by flashing the stock ROM build number S5830DXKT5 if you prepare by using Odin flasher tool instead via online in Samsung Kies server. This will upgrade your device to Android 2.3.6 Gingerbread the most latest firmware update this year. This is an update from the previous version with build number Android 2.3.4 S5830DXKPD. So check out your device firmware info by typing *#1234# to know what Android version your Galaxy Ace runs.

This for Asia version of Samsung Galaxy Ace specifically for Singtel network provider in Singapore users but can also be used by nearby South East Asian countries for it has the same firmware build, the only disadvantage is that, you'll get the Singtel's default CSC file and you will get some issues updating on Kies in your areas. For European version, you can try to upgrade to Android 2.3.6 by using the Nordic countries firmware S5830XWKT7 and or the Russian S5830XXKPP which is both an Android 2.3.6 also.
Do not use the stock Asian stock ROM, unless you are in Asia region for it got the Asian support languages and applications.

Disclaimer: Hackerzadda shall not held responsible if anything happens to your device by following this procedure. Proceed at your own risk. This is not advisable for beginners, for advance users and experts alike use only.

This is a manual method, so you need to grab the official build firmware update S5830DXKT5 in Odin flashable stock ROM and then the Odin multi-downloader program.
Grab it here at sammobile firmware page.
Stock ROM: S5830DXKT5_S5830OLBKT3_XSO
Password: samfirmware.com (if the password don't work it means your download is corrupted, it already proven and works for us)
ODIN: Odin_Multi_Downloader_v4.38.rar
You'll also need the OPS file for it has not included in the package.
OPS: Cooper_v1.0.ops

Once you download the file, extract it then you'll get the S5830DXKT5_S5830OLBKT3_S5830DXKT4_HOME.tar.md5 file.
There is also another file labeled 'SS_DL.dll' - which is not going to use on this process. 

Important: Do the following before proceeding;
- Back up all the important files stored from the device. (Although we are flashing a single file here, it means that no wipe will take effect but its better to be prepare if something went wrong.
- Ensure that the battery is at-least 50% charge, much better if it's fully charge. (This will prevent your device from bricking due to power failure)
- Use a good conditioned and a working USB cable for your Galaxy Ace.
- Your PC or laptop must run on windows OS with a good USB serial port connection.
Sometimes flashing fails because of bad PC/laptop USB serial ports.

1) Now, run Odin on your desktop.
2) On ODIN click the OPS button and load the Cooper_v1.0.ops file on it.
3)  Hit the One packaged in the checkboxes options (the Auto reboot and protect OPS remains to be checked, then at the lower part of Odin click on the One Packaged button then select and load the
S5830DXKT5_S5830OLBKT3_S5830DXKT4_HOME.tar.md5

4) Set the Samsung Galaxy Ace in Download Mode:
Turn the OFF the phone or remove the battery for a couple of seconds then put it back again. By pressing Volume Down+Power+ Middle keys simultaneously. The phone will then reboot into download mode.

5) If the device is already displays the download mode, connect the phone to PC, on ODIN window the COM Port mapping turn to color yellow and indicates that the device is already 'added' - means connected.
6) Once the connection set up is okay, begin the flashing by hitting the 'Start' button.

It only takes around 4 to 5 minutes to complete, a progress bar on the left side of ODIN will show you the downloading progress. A word "PASS" will display once it finishes.
It's time to unplug the phone from PC, then do a factory data reset to clean all data caches and have a fresh firmware installed, you can do this by Recovery Mode button - Home + Power Button, then toggle on using the volume button and select Wipe Data/ Factory Reset or by typing this code *2767*3855#.
To check the newly installed firmware update - by typing *#1234#.
You might also need to re-confingure you APN settings again if having wifi or internet connection issues. 
Source:-http://droidangel.blogspot.in