"host process for windows has stopped working" please help!

Hi everyone, I have just started encountering this problem very often with my laptop, im running vista home basic, and it keeps on seeming to happen shortly after i boot up my computer.
Recently I installed 2GB Crucial RAM (2x1gb) (I had 2x512mb before) and soon after this problem, along with a few others have started happening, for example, i can hear the hard drive clicking and whirring a lot louder than usual - which makes me think that i may have knocked it or something when i put it upside down (?), anyway, on the Problems Report and Solutions page, it says to look in event viewer, and i found the culprit file being C:\Windows\Prefetch\WINRAR.EXE-BA8CDB31.pf
I did try putting the old ram back in to see if it would have any effect - but it definately wasnt the ram.
So what can I do?? can I delete this file to stop it trying to access it? (I no that will probably be a very stupid thing to do) or is there some way i can fix it? - or do you think my hard drive may be damaged?!

Anyway any help would be much apprecciated.
here is my comps spec -

Dell Vostro 1000
AMD Turion X2 64 TL-56 1.8Ghz
2x1gb RAM
120HDD
32 bit Vista home basic
Iis about 8 months old.