Call of Duty 5 PC version

I have COD 5 on a PC with 2 gig ram, Get force 7600 GS video. 6.1 surround sound, and AMD 3200+ processor. Originally the game did fine, then the patches worked fine up to the 1.5 and new map pack. I do not know exactly when things started going wrong, because I do not like tanks that much, however when I tried one it would literally sink into the map, no one else could see this except once. I can ride in a tank someone else is driving no problem.
I have tried all the perks, and the satchel charge does not give any charges just the detonator. Also recently after installing the 1.5 patch with the new maps, i noticed the sniper rifle which is my main weapon seems to be dead center and then no kill. this comes and goes throughout map, the overkill first weapon works fine if I hit them they die, it also has a scope.
has anyone experienced this or similar actions on the cod 5 game? once the game crashed for no reason then I lost my experience and saved weapons selected and had to start over. I have since gotten back to the last level in fact I have enough points to make Prestige level two or three. I need to know if there is an easy way to reload the game and save the in game rank and experience level?

I play COD5 online with friends a lot*, and everyone's suffered a lost profile at some point. Sadly, it's not a rare thing. If you go here, there's a profile backup tool with instructions: http://www.mapmodnews.com/article. [...] ofile-rank
Unfortunately, you are skirting the lower reaches of the spec list for COD5. In my experience, COD5 is also very twitchy when it comes to ping (unlike, say, some Valve games). If your connection is a bit off (much over 100), then it does tend to go to hell.

* Even though I'm sick of the bloody game, tbh