Try leaving it at 2GB of ram during the installation,then put it ack in of it works.
Also get your motherboard,bios,graphics
driver etc and load them before you begin the installation by using the advanced option to install.
Make sure your hard drive is set a NTFS/Active and Primary with Partiton Wizard.
Get the boot disc,its easiest.
Use resolution 1 (enable num lock and press 1)
And ok to the other warnings.
Re format as Primary and NTFS -Click apply
Right click the hard drive- Set as active-Apply
Boot up form the Windows 7 disc a install after loading the
drivers.
Let us know how you get on.