Windows Installer cannot be accessed

This started happening after i tried to return my laptop back to factory settings, and got a copy of windows 7 from my friend (not sure how authentic the copy was), but anyway i installed it, and after setting up the computer i realized for some reason none of my drivers were installed. For example (usb drivers, drivers that allow the internet to work, etc, etc) After realizing this i went and found all the cds that came with my Dell Inspiron N5040 and i found a cd labeled Dell Drivers or something along those lines, and went ahead and installed whatever i could, and most of the drivers installed. The only problems i am having are whenever i try installing something that requires windows installer, it doesnt install and gives me a message that says windows installer cannot be accessed, and the other problem is when i put my computer to sleep or hibernate, my wireless stops working and i need to run windows troubleshoot and it *resets* my router and it starts working. The MAIN PROBLEM is the WINDOWS INSTALLER CANNOT BE ACCESSED, if anyone can help me with this that would make my day.

Some additional information: I have tried all the solutions on other websites and its just not working.


Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: Intel(R) Core(TM) i3 CPU M 390 @ 2.67GHz, Intel64 Family 6 Model 37 Stepping 5
Processor Count: 4
RAM: 3894 Mb
Graphics Card: Intel(R) HD Graphics, 1723 Mb
Hard Drives: C: Total - 461838 MB, Free - 273227 MB;
Motherboard: Dell Inc., 0R08PM
Antivirus: avast! Antivirus, Updated and Enabled