STOP:c0000221 {Bad Image Checksum}

Try loading in Safe Mode and disabling as many Startup programs is MSCofig as possible. You could also try rolling back with System Restore, again in Safe Mode. From there try uninstalling any software that was loaded prior to the problem.
Another route is trying to load Windows on top of its self as to correct any corrupted files. Then try testing your RAM one DIMM at a time, one slot at a time to eliminate bad RAM.
Finally a clean install may be required, then going back to RAM isolation if occurs with a clean Windows setup.

This error is not the same as a CMOS Checksum Error, which refers to corrupted values of the CMOS settings, the ones you set through the BIOS setup program. This error means the contents of the BIOS code itself are damaged.

During the boot process you will see on the screen to press delete to enter setup
Press and hold delete during the boot up process to enter BIOS you can load failsafe defaults or load optimized defaults ,press escape then press f10 to save to cmos to restart
click start control panel date and time you can make your adjustments to the date and time from there also right click on the date and time on the bottom toolbar (bottom of screen) you should see Adjust date and time tab
hope this helps you

Yes it may be possible, installing and updating antivirus may have figured our corruption in urlmon.dll deleted the file or did some changes due to which you are getting the critical error

You can try 2 things,

1. Restore earlier settings, which may uninstall your antivirus and you need to install again. But if this works recommend you to first scan the system with free standalone antivirus availalable and then install your version of antivirus. Try following link

http://go.trendmicro.com/housecall7/HousecallLauncher.exe
http://www.trendmicro.com/ftp/products/rootkitbuster/RootkitBuster_2.80.1077.zip
2. Repair the URLMON.DLL file

1.Insert your Windows XP CD in your CD-ROM drive and boot your computer from the CD.
2.When the Welcome to Setup screen appears, press R to open the Recovery Console.
3.When prompted for an administrator password, type the password and then press Enter. In case no administrator password was set, just press Enter.
4.At the Command Prompt, type the following command and press Enter
cd %systemroot%\system32
5.Next, type the following command to rename the urlmon.dll file and press Enter.
ren urlmon.dll urlmon.old.dll
6.Now, to restore the original urlmon.dll, type the following command and press Enter.
expand [CD drive letter]:\i386\urlmon.dll %systemroot%\system32 /Y
7.Next, type exit and press Enter.
8.Restart your computer.

3. Repair complete OS. You will need XP CD
Boot from CD and follow the instructions to repair the OS

Just FORMAT it... But if you scare of losing your info and data, then choose the option to REPAIR the windows installation. Or what you can do is do a checkpoint system restore. You will have to go through much more headachs to resolve it.

Most of the time that problem occurred because of an unsuccessful installation of a program or app. Or you might of deleted a common file accidently...

your windows is surely corrupted.. install your windows again... if you dont know how to install your windows...contact me....at ([email protected])

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Greetings,

When you upgrade your computer to Windows XP, you may receive an error message that is similar to one of the following: C0000221 (Bad Image Checksum)
-or- STOP: C0000221 - Bad Image Checksum in ModuleName
-or- STOP: C0000221 - Bad Image Checksum. User32.dll is possibly corrupt. The header check sum does not match the computed check sum.

Please go through the below mentioned link:

http://support.microsoft.com/kb/326687

Boot to recovery console (Boot to Windows CD, Press R at 1st prompt) run CHKDSK /R

You most likely have bad RAM. If you have two chips, pull one out and run the laptop on a single stick. You may need to alternate the sticks just incase the non-working one is the one you left in the laptop.

Try re-starting your pc and tapping the F8 while it starts up and try getting in through "Safe Mode". If you can get in click "Start", "Run" and type "cmd". Hit OK. At the dos promt type "sfc" and let windows check your files.

Please give more info about this.

Try to reformat your Hard Drive and install it againg freshly. This might do the work.