Error on startup

After a period of time

Having scoured several topics in relation to this issue, I am still none the wiser and like many pledging for some guidance, I thought it best to post here.
Some quick Background Info;
I made this computer using my old Powersupply ( Jeantech 500W) and Harddrive. I had previously used the graphics card in my old setup and had no issues. This was XP, different motherboard, processor etc. I formatted the Harddrive and installed Windows 64bit and installed all the new parts.
Drivers are all up to date except the motherboard. (Of which the CD couldn't be detected)
Specs;
Powersupply: Jeantech 500w
Motherboard: Asus P5Q SE plus
Graphics Card: Sapphire 4850 512mb
Ram: 4GB
Processor: Intel Q6600
The Issue;
When I turn on my computer, at the login screen I receive small blocks of colour that do not match the screens intended picture. On the log in screen this is normally minimal, but on my main desktop this will nearly cover the screen intermitantly. Sounds bad? But it will either fix itself in time with the "Windows has recovered the driver Atiamtag" Or, I pop open the Chess program and on load up this clears the issue.
It seems the issue is prior to the graphics card starting?
Old Issue I resolved;
I use to receive this problem AND my graphics would occasionally blackscreen for a second and say ATIAMTAG has recovered. I disabled the ATI Control Center and this has fixed this issue. (Except on startup if I don't load chess!). This has been the only working solution I could find online.
What I think
I think it's a mobo issue, however I can't think why it would be this? The motherboard works perfectly fine in all other aspects and I'm pleased with my computer as a whole. This is a small inconvience but is preventing me from overclocking my Q6600 to a higher clock speed. I am however elsewise out of ideas and how to tackle this issue.
Any help would be appreciated!
(Yes, I've uninstalled and reinstalled the graphics drivers several times whilst attempting to fix the old graphics driver issue!)

After a period of time

Having scoured several topics in relation to this issue, I am still none the wiser and like many pledging for some guidance, I thought it best to post here.
Some quick Background Info;
I made this computer using my old Powersupply ( Jeantech 500W) and Harddrive. I had previously used the graphics card in my old setup and had no issues. This was XP, different motherboard, processor etc. I formatted the Harddrive and installed Windows 64bit and installed all the new parts.
Drivers are all up to date except the motherboard. (Of which the CD couldn't be detected)
Specs;
Powersupply: Jeantech 500w
Motherboard: Asus P5Q SE plus
Graphics Card: Sapphire 4850 512mb
Ram: 4GB
Processor: Intel Q6600
The Issue;
When I turn on my computer, at the login screen I receive small blocks of colour that do not match the screens intended picture. On the log in screen this is normally minimal, but on my main desktop this will nearly cover the screen intermitantly. Sounds bad? But it will either fix itself in time with the "Windows has recovered the driver Atiamtag" Or, I pop open the Chess program and on load up this clears the issue.
It seems the issue is prior to the graphics card starting?
Old Issue I resolved;
I use to receive this problem AND my graphics would occasionally blackscreen for a second and say ATIAMTAG has recovered. I disabled the ATI Control Center and this has fixed this issue. (Except on startup if I don't load chess!). This has been the only working solution I could find online.
What I think
I think it's a mobo issue, however I can't think why it would be this? The motherboard works perfectly fine in all other aspects and I'm pleased with my computer as a whole. This is a small inconvience but is preventing me from overclocking my Q6600 to a higher clock speed. I am however elsewise out of ideas and how to tackle this issue.
Any help would be appreciated!

(Yes, I've uninstalled and reinstalled the graphics drivers several times whilst attempting to fix the old graphics driver issue!)
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