trouble after reinstall windows7 need help please

I really need some help...i have reinstall windows 7- 3 times. None have worked.
i first system restored to earlier time. It work for awhile then stopped. Next i went through the f8.using dell databackup disk, again worked for days and then stopped.. last night i tried the system recovery disk made when first got system. I had tried them before but it wouldnt read them..last night it did. Retore to factory settings. But when i was looking at the computer panel i no longer have the d drive...sending a picture. orginaly there was the c with 56 gigs and d with rest. now d is unalloted. I would like to partition c bigger but thats later. I thought virus but i have ran all online scanners and no virus showed. I have ran all the diagnostics dell and microsoft installed. No problems..
My problems--1. when i turned on pc today, i am getting same message that made me do first restore..
"Realtek PCI FE Family Controller etc..PXE E-61 media test failed
PXE-M0F exiting PXE ROM"
exit reboot or install boot media"
2. what happened to d drive, make it useable again?
3. How do i make the install stable
I have my pc set at f2 to boot to hard drive. Each time i start pc i have to redo this even though i keep saving configuration to hard drive...when using dvd i f12 to boot to dvd but always reset it...so
what do i do now...my pc will not stay set to boot to hard drive nor is the d drive there...i used the methods decribed-toubleshooting boot failure.
system- Dell Inspiron M5010-
AMD Phenom II P920 quadcore 1.60Ghz-
4.00GB-
64-bit os-NTFS
Windows 7 Home Premium sp1
version 6.1

Follow these steps to get a perfect Clean Reinstall - Factory OEM Windows 7 with Special Notes to Dell Owners at end to understand how the OEM partitions are best handled.

The "Realtek PXE media test failure" error prompt sounds like the BIOS in trying to boot into a Network choice instead of HD. Make sure HD is set first to boot in BIOS setup. Then trigger the DVD or flash stick installer using Dell F12 key.

Do you still have Dell Diagnostics available from F12 menu? If not then you can delete all partitions before reinstall since you already have lost Recovery functionality if not content.

Appreciate the answers...Mark will go back to motherboard site and check...
Greg...for now will leave it alone and see if this reinstall stays. If not then will to OEM reinstall as u suggested...I found and partitioned hd to get a d drive..
I still have the Dell Diagnostic ..it found no problems..