After hours of hard work, I've finally managed to reinstall them... I've tried several times to uninstall and install again and vice versa but here's what I've did and worked:
1)I've uncompressed the Catalyst 10.4 Files somewhere on the HDD.
2)I've uninstalled the video card driver and VGA Adapter in Device Manager.
3)I've restarted and when the "Found new device"box popped up, I've set the path to the uncompressed ATI drivers path and let the wizard install them. After successfully installed them, I've restarted the PC and installed ADM(acer device manager for my new monitor), restarted, and then installed Catalyst.
4)After restarting once more, all was good.
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hew:
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1)OS is Windows XP SP3
2)In device manager it said that the drivers were not installed properly or something like this.
3)Gigabyte 5770 1GB
4)Well, I was just on the net, then when I've tried to click "properties" on the desktop, there was an error of some dll and the something about Watson PostMortem debugger. Then the taskbar wouldn't work so I've restarted. The resolution was low and the ati error popped up.
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That's about all! Hope it helps if there are more people in my shoes.