thank you all for your replies!!
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Saltgrass : i dont really understand you about the
driver order,bios and that stuff,my knowledge about that isn't the best,i could use some explanation. And i tried to start windows 7 with startup repair, but without succes. I'm planning to buy more RAM (i have 2gb,i will buy 2gb more) and i would upgrade to windows 7 64 bit. then i can install xp first.
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theog : i posted my problems there , but the admin moved my post here,he thought i would get more help here

thanks anyways

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gregrocker : i have started windows 7 .... i haven't tried Startup Repair repeatedly ... but thank you for the tip
and a question : so what what is the best way ... to install xp and then 7 ? but what to do with the hard disk partition and formating. if i install xp first on one partition should i leave the other one and format it with the windos 7 dvd , and vice versa.should i make partition for xp , and the other partition to make when i insert windows 7 dvd , so to leave unallocated space....
sorry for my english