There is a problem with Black Mesa which seems common to anyone running an Athlon Xp system.
When trying to run Black Mesa the following error occurs:
‘Could not load library client’.
That this affects Athlon Xp users seems to indicate that the client.dll (and server.dll?) does not support SSE, which is what these processor sets use as opposed to the later SSE2 etc.
These machines, mine and many others, are technically capable of running the game as swapping the client.dll in the BMS .bin for one out of the SDKbas2007, sourcetest .bin, allows the game to run and begin, but you cannot progress beyond the end of the Tram ride or use the options menu as the .dll is wrong. But it shows that the machines can run Black Mesa and SDK2007.
Others have speculated that this means that the .dll’s need recompiling for SSE.
Link to forum thread: https://forums.blackmesasource.com/showthread.php?p=495973
Minidump attached
PC specs:
AMD Athlon XP
Model number 3000+
CPU part number AXDA3000DKV4D is an OEM/tray microprocessor
Stepping codes ADYHA AQUCA AQXCA AQXDA AQXEA AQXFA AQYFA AQYHA AQZEA AQZFA KQYHA
Frequency 3000+ (rated)
2167 MHz (real)
Bus speed 333 MHz
Clock multiplier 13
Package 453-pin organic PGA
1.95" x 1.95" (4.95 cm x 4.95 cm)
AMD Package numbers 27488, 27493, 28103
Socket Socket A (Socket 462)
Introduction date 10-Feb-03
Microarchitecture K7
Processor core Barton (Model 10)
Manufacturing process 0.13 micron copper process
Data width 32 bit
The number of cores 1
The number of threads 1
Floating Point Unit Integrated
Level 1 cache size 64 KB code
64 KB data
Level 2 cache size Full-speed exclusive on-die 512 KB
Multiprocessing Uniprocessor
Features:
MMX technology
SSE
3DNow! Professional
Additional PC info:
1 Gb RAM
512 Mb Radeon X1950 Pro graphics
Really hope this can be fixed. 
hl2_4104_crash_2012_9_16T15_32_7C0.mdmp (62.6 KB)