E5510 Windows 7 pro 64 bit with 8GB not launching OS

Hi All,

I have a Latitude E5510:

Intel® Core™ i5-560M Processor (3M Cache, 2.66 GHz)
Windows 7 32 bit
4GB(2X2GB)1333MHZ DDR3 DUAL
250GB SERIAL ATA (7200RPM)

1rst harddisk malfunctioned and i replaced it for a SSD Crucial, installed original OS worked fine!!
(upgraded bios from A05 to A16)
2nd needed more internal memory. googled and saw in a this forum
Compatible with Memory Type: DDR3 PC3-10600, DDR3 PC3-8500, DDR3 (non-ECC)
Maximum Memory: 8GB Slots: 2.
Ordered 2 4gb kingston KTD-L3BS/4G. installed them and Bios recognized them, so far so good.
Windows also did its part and i could see 8gb installed in the system specs.

For a new software i needed to installed a 64 bit version of windows.After reading online, it was possible to reinstall the laptop using Win7 64 bit instead of 32 bit and I could actived the 64 bit verion with the same oem lic key.

Inserted the new downloaded Iso dvd with win7 64 bit, but it kept going into a loop, it red the files and after the windows logo it rebooted and started again.

I replaced the new 8gb memory with the "old" 4gb and i could installed win 7 64 bit. all ok installed all drivers from dell site.
After all was working fine i replaced the memory back to 8gb. but it rebooted untill the windows logo and then i saw a cursus on the left top screen and the laptop kept going into this loop.

While writing this post i had an idea of sending the memory back to the supplier and replace them with a dual DDR3 kit.
But if someone have a trip and trick for this please let me know.