Odd...

Recently I had a hard-drive failure that resulted in what should have been a relatively short string of repairs. The pertinent information is as follows:

Computer: Asus EeePC 1201N Seashell (yeah I know, cute), relevant specifications can be found here: [http://www.asus.com/Eee/Eee_PC/Eee_PC_1201N_Seashell/#specifications]

Upgrades:
Hard Drive - "upgraded" from the stock hitatchi HD which burned out to a Western Digital drive with the same specifications [WD SATA2 WD2500BEVT]
Memory - May 2010: upgraded from the stock 1gb to a 2gb stick from another computer, worked just fine. [GSKILL F2-4200CL4S-2GBSQ]
November 2011: purchased an identical 2gb stick of ram to get up to 4gb of ram. Just for kicks.
Running Windows 7 32-bit.

Installed the new hard drive no problem. Re-installed Windows 7 with a few hiccups (BIOS compatibility BS, over it now). Put the BIOS back to normal, tried to install the new 2gb stick of RAM and... the damn thing freezes. Sometimes it doesn't make it to the 'starting windows' page, once I got all the way to running performance score through the control panel before it froze. Either stick by itself in either bus works fine, and I am currently running Windows 7 in safe mode with both sticks installed and that also is OK. The BIOS recognizes the full 4096mb. So...WTF? This motherboard is supposed to be able to handle up to 8gb, other seashell owners have successfully upgraded their ram, both sticks obviously work and both busses obviously work, and again the sticks are absolutely identical in specifications, down to the model number, and they obviously are capable of working in tandem because they're working now in safe mode but as soon as I boot back into normal mode, the screen freezes and I have to shut the machine off manually.

 

Try testing each stick seperately with memtest 86. It sounds more like a driver issue. Anything showing up in Device Manager?

 

I haven't worked on an eee PC 1200 series yet; however if it is like the 1000 series (removing the keyboard and some internal cables to access the hard drive), the cable reconnection can be tricky. If augie's tip doesn't work, recheck the connections of any cables you had to disconnect/reconnect in the HDD replacement process.