Do you have a different PC you can test the 1800 in? If so do it.
If no problem on different PC .
Download said to be best CCC suite to desktop.
Then uninstall the CCC and Video Driver reboot run Driver Cleaner Pro and select multiple files box and add CCC and ATI WDM run the deletions .
then reinstall all the .NETS and patches with required reboots.
Then reinstall the Downloaded (said to best CCC for your card)thats on your desktop .
Do an advanced install and deselect WDM and install every thing else .
After install is finished select NO to reboot.
Then go to C:\ATI\SUPPORT\7-10_xp32_dd_ccc_wdm_enu_53250\Driver\WDM_ALL and run the Setup.exe to in stall the WDM . (reason for this little obstacle is I have seen many issues getting the WDM to install in the CCC script)...
Then reboot.
Then download DX9c and reinstall.then reboot and run ATITOOL to turn fan to 100% and only use ATITOOL for that function(for now) and test for crashing.
Please report back