This is a report from RivaTuner. I think it pretty much says, that I have a problem...
---------------------------------------------------
Northbridge information
---------------------------------------------------
Description : VIA KT266 series
Vendor ID : 1106 (VIA)
Device ID : 3099
AGP status : enabled
AGP rate : 1x 2x 4x supported, 4x selected
AGP SBA : supported, enabled
AGP FW : supported, enabled
---------------------------------------------------
Display adapter information
---------------------------------------------------
Description : NVIDIA GeForce4 Ti 4600
Vendor ID : 10de (NVIDIA)
Device ID : 0250
Location : bus 1, device 0, function 0
Base address : e8000000
AGP status : enabled
AGP rate : 1x 2x 4x supported, 4x selected
AGP SBA : supported, enabled
AGP FW : supported, enabled
---------------------------------------------------
NVIDIA specific display adapter information
---------------------------------------------------
Graphics core : NV25
Bus type : AGP
Memory bus : 128-bit
Memory type : DDR (RAM configuration 0c)
Memory amount : 131072KB
Core clock : 150.000MHz
Memory clock : 162.000MHz (324.000MHz effective)