Question Winlogon crash when transferring data over Lan

[MrNope]

Hi,
for no better use I have my old Optiplex 755 set up as pseudoNAS. It runs windows 7 pro, I have shared folders over LAN. Issue is that when I'm transferring bigger ammount of data (1GB+), the winlogon crashes and system cuts off all incoming/outgoing data over LAN. RDP cannot be used at that time and I cannot log into the system even the direct way by going to the machine and use keyboard and monitor. HW is anciend but it's not maxing out while data transfer and there is no active antivirus at this time.

HW setup:

C2 quad Q9400
4 GB DDR2
Radeon HD 2400 XT,
stock MB
network over MB gigabit LAN

Thanks for all hints

 

[MrNope]

Update: Before I reinstalled the system, I wanted to investigate what is the exact issue. The logon failure message was just consequence, not the cause. The main issue is the RAM. All files transfered over LAN are cached into the RAM, and they stays there until the system crashes because of the lack of memory. I was playing with the superfetch, prefetch, that suppose to cache these files, but no change. Offline file sharing mode and caching settings in drive menus also didn't help. I downloaded RamMap and even the "Empty Standby List" option didn't do anything. "Mapped files" are still firmly wedged into my memory. We can try absolutely everything, any ideas?