Low FPS @ HL and are there Alt. GL Driver's ?

Hey guys my problem :

FPS in HL and in the Mods of it are F__cking LOW > about 15->50>99 but 99 is the highend when I stand in front of a wall.
When I look on some Models (like in DOD 5 Soldiers I get 30). Ive had to reinstall Windows ME some days ago because there was a virus in the files of Win ME I only deleted the Windows Rootdir and the Subdir’s.
After that reinstall of drivers and so on well UT 2k3 runs good in D3D and Neverwinter Nights too (all things high @ NWN - Q3 Demo001 1024 X 32 all high 73FPS 3D Mark 01SE 5100 1024 x 32 ) new Detonator Drivers DX 8.1
but in Half Life runs like **** …
Ive reinstalled it too but no results I tried many console cmds but no result …

My Machine :
CPU : AMD Duron 900MHz @ ~1067MHz
RAM : 576 MB SD-Ram 100mhz
GFX : Winfast A 250 GF 4 Ti 4200 (43.00 Deto)
OS : Windows ME (no updates tweaked with Winboost)
DX : Direct X 8.1 Final

Are there Alternative Open GL Drivers for nVidia GFX cards ? or some like that ?

I have exactly the same problem, and it is EXTREMELY annoying.

System specs:
Win Xp Pro
Geforce 3 Ti 500
P3 3.0ghz 800mhz FSB
ASUS P4C800 Deluxe Motherboard

It’s been happening ever since I formatted winxp ~3weeks ago.