
Your only options are running it in software (doesn't look as nice, only left handed models in CS, slower rendering of dynamic lights/flashlight) or OpenGL. This question was asked in 2013 - that same year they had removed direct3d support from the game (and it's derivatives/mods like CS 1.6, TFC, etc). I would say that it's due to the video rendering mode/drivers/graphics chipset. Harddrive I/O mode might not be set correctly causing poor performance (AHCI vs ATA mode for SATA drives).Harddrive becoming old, check SMART values.Too slow a harddrive for this game, or some other program is just performing a lot of drive I/O (bit-torrent?).Too little RAM available, something's hoarding RAM and Trashing the system?.Also check for CPU temperatures and thermal throttling! ( OHM).Check the power plan/power saving options for CPU clock-scaling limits!.Slow CPU or something's eating up CPU time.Driver updates might fix performance issues for newer games (I've heard stories about new drivers causing worse performance for older games too (forced obsolescence), but that's anecdotal.).

(My gut says the latter seems to be the issue here!)
