Windows 7 - Windows 7 vs. Laptop installation issues

I´ve tried clean installation of Windows 7 32bit on my DELL Inspiron 6400 laptop.
My hdd has only 1 partition so i don´t think that is the issue.It all went smoothly: copying, expanding, installing features and updates.. no problem. Then, the system showed me message - failed to log on and rebooted itself. I´ve tried everything with no results.I´ve tried upgrade advisor which did not found any problems, i upgradet my Bios.I´ve also tried to install it from Usb flash drive using original microsoft software.tried external dvd drive but nothing works.I don´t know what else to try.

PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

THANK YOU, I´m desperate

What error message did it show?

Did you install by booting from the disk, or run it from another OS?

You might try booting from the disk or USB flash, choose Custom>Advanced tools and Delete all, create one New partition, then Format and install.

I've installed it by booting from USB flash as a clean installation, i've formated my hard drive aswell.I don't have any other OS installed on my system.it showed this message - "logon failed".this appeared just before my desktop was about to appear.as i've passed many forums it seem that i'm the only one with this problem.i cannot repair the boot through the system repair aswell.tried bcdedit with no results.

Ok boot into the installer's Repair my Computer console and see if it finds a valid installation to repair.

If so, go ahead and run Startup Repair repeatedly and report back what occurs.

How old is this Dell? Have you talked with their tech support before? If less than a year old, you are still owed tech support from Dell.

If they tell you they don't support Windows 7, then ask them if there is any reason why Windows 7 cannot run on that model (like a BIOS block).

Tell them you are prepared to reinstall Vista in order to get Hardware support, and inquire about recovery disks if you didn't previously make or receive them.