Around the end of July, my computer suddenly began working very slowly. If I tried to open any program, it would take a very long time to do so, if it did at all. Most programs simply crashed. Several times, the computer stopped responding, and I restarted. Over the course of the next week or two, the performance gradually improved until I could run some programs again, even at almost-normal speed. My first priority at the time was to scan the computer with AVG to try and fix the problem. The problem, however, did not go away, although at one point AVG found a backdoor Trojan on my flash drive. I assume it removed it, though I'm not positive as I'm not very familiar with this type of thing. Now, many of my programs didn't work. If I attempted to open them, they crashed and I got the typical program-not-responding message, or in some cases, dialog boxes offering to send error reports to the respective companies. Among these programs were Internet Explorer, Mozilla Firefox, Windows Live Messenger, ROBLOX, Windows Sidebar, Google Sketchup, Secunia PSI, SimpLite-MSN, Java Platform SE binary, and Speech Recognition. I also repeatedly get the same message for Microsoft Feeds Sychronization. Also, whenever I restart, I get the error message listed below as Error Message 1. I lost all of my email, though I was still able to send and receive it. Soon after my email was recovered. I also found the downloaded files for Mozilla Firefox, and using those I was able to reinstall Firefox, which now works fine. The rest of the programs, however, continue to crash when I try to open them. This problem details I get when IE crashes are listed below as Error Message 2. Since then I have made several attempts to fix the problem, including clean booting, running DDS.scr, running the System File Checker, and System Restore (which doesn't work because all of my restore points are after the problem started).
Error Message 1: Error loading C:\Windows\System32\NvCpl.dll
Invalid access to memory location.
Error Message 2: Problem Event Name: APPCRASH
Application Name: iexplore.exe
Application Version: 8.0.6001.18813
Application Timestamp: 4a6621ae
Fault Module Name: WININET.dll
Fault Module Version: 8.0.6001.18813
Fault Module Timestamp: 4a6638d8
Exception Code: c0000005
Exception Offset: 00087149
OS Version: 6.0.6001.2.1.0.768.3
Locale ID: 1033
Additional Information 1: fd00
Additional Information 2: ea6f5fe8924aaa756324d57f87834160
Additional Information 3: fd00
Additional Information 4: ea6f5fe8924aaa756324d57f87834160