I consider my system to be very bottom of the pile. It's old. It's slow but it plays AH with all the bells and whistles turned off except for "bump mapping" smoothly.
You can pick out the particulars from the DxDiagnostic text file:
Operating System: Windows XP Home Edition (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_gdr.090804-1435)
Language: English (Regional Setting: English)
System Manufacturer: GBT___
System Model: AWRDACPI
BIOS: Award Modular BIOS v6.00PG
Processor: AMD Athlon(tm) XP 2600+, MMX, 3DNow, ~1.9GHz
Memory: 1024MB RAM
Page File: 367MB used, 1327MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode
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DxDiag Notes
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DirectX Files Tab: No problems found.
Display Tab 1: No problems found.
Sound Tab 1: No problems found.
Music Tab: No problems found.
Input Tab: No problems found.
Network Tab: No problems found.
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DirectX Debug Levels
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Direct3D: 0/4 (n/a)
DirectDraw: 0/4 (retail)
DirectInput: 0/5 (n/a)
DirectMusic: 0/5 (n/a)
DirectPlay: 0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow: 0/6 (retail)
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Display Devices
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Card name: NVIDIA GeForce 7800 GS
Manufacturer: NVIDIA
Chip type: GeForce 7800 GS
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_00F5&SUBSYS_1FA419F1&REV_A2
Display Memory: 256.0 MB
Current Mode: 1024 x 768 (32 bit) (60Hz)
Monitor: Plug and Play Monitor
Monitor Max Res: 1600,1200
Driver Name: nv4_disp.dll
Driver Version: 6.14.0011.9038 (English)
DDI Version: 9 (or higher)
Driver Attributes: Final Retail
Driver Date/Size: 7/14/2009 13:54:00, 5842816 bytes