So I've been having a hard time fixing my girlfriend's Asus netbook.
Asus Eee PC 1005HAB
Windows XP Home (SP 2)

It's about three months old.

First, it started giving stop errors, I thought it was memory related. I got a few more stop errors, ran a memory check and tested different RAM modules. Windows stopped booting before I could pinpoint the problem. Now when I try to boot, even in safe mode, I get an error saying WINDOWS\SYSTEM32\CONFIG\SYSTEM is missing or corrupted.

After failure getting Linux to boot from usb, I went and bought a hard drive enclosure, and booted Linux from CD to recover the data. This worked fine. I saw no issues, hardware related or otherwise, when I was booted in Linux or during POST.

I borrowed an OEM XP disk (SP 2), since the netbook came with a recovery disk but my gf promptly lost it. Before getting to the fabled "hit r to boot recovery console" prompt (which I have never seen because this is my first tinkerings with recovery console), I get a stop error. I tried a few times. It happens after about 3 minutes, as Windows is unpacking and preparing to install. After 3-4 minutes, when it's on the plain blue screen loading setup files, I get a stop error:
0x0000007B (0xF898D524, 0xC0000034, 0x000000, 0x000000)

Okay, so I thought it might have to do with the fact that the XP disk was OEM, probably loading the wrong drivers and such. So I burned Windows Recovery Console (I downloaded the .iso) and tried booting from that. No dice. I got a different stop error this time:
0x0000007E (0x0000005, 0xF8995208, 0xF8994F08
Pci.sys - Address F85490BF base at F8542000, DateStamp 3b7d855c

What the heck do you think caused these problems? And how can I fix this issue so Windows boots, and prevent further issues or complications?

A word about the netbook's history: It belongs to my girlfriend, who has minimal computer experience and doesn't seem to care too much about maintaining the netbook carefully so it continues to operate efficiently
But she did have anti virus (Webroot) and firewall (Comodo), and I ran MBAM frequently. I kept it pretty well maintained, and besides lagginess in applications (I was going to upgrade the memory), it was running without fatal symptoms, or any symptoms, really

If possible update your netbook's BIOS to start with.

Also this error code can be caused by faulty device driver(s).