The way i see it you have 2 choices
download steam, a legal and safe application which is used by over 4 mil diff ppl a day:http://store.steampowered.com/
create an account with an email
goto the store tab
in the search bar type Left 4 Dead
and click the l4d1 icon that results from the search
press the green button add to cart
then press proceed to checkout
boom you have the legal, 100% supported, re-downloadable, and error free copy of l4d1 complete with all textures, 100% working online play, support from community, and the ability to add and play with friends as well as play any map or use any mod without error (so long as the map or mod doesnt contain the error itself) now for just 20 bucks that is a good buy even with the fact it constantly goes on sale along with l4d2. Nobody that can afford internet, or a computer, cant afford 20 dollars of 1000 hours of fun and enjoyment (slightly over-exaggerated, experience may vary)
-please note as rayman said a legal retail CD will work just fine, you will still need steam to activate it and play online though.
you can continue to use your version which comes with the following; shitton of errors, lack of community support, manual patches, lack of ability to add and play with friends, lack of online experience(can get online play but it sucks as theres never a real server with real ppl) the possibility of virus after virus smashing down on your computer and shitting on your desktop, multitudes of texture errors like the ones youre complaining about, and the fact you are breaking the law.
Im not going to choose for you, but the moral, ethical, smart, and good choice is choice number 1.