HELP NEEDED! CAN'T INSTALL PROGRAMS (WIN7 64-bit)

would greatly appreciative if I could get some assistance/feedback regarding my current problem. for about the last month, when I try to install anything, I am not able to do so. get a variety of error msgs (i.e. Install Failed, initiate install failure, cannot access Users/Public/Desktop, etc). no clue why I'm having this annoyance, def have not tinkered with any system settings/deleted anything important/etc. if so it was unintentional. I use IObit Advanced System Care quite frequently to keep my PC running smoothly, maybe that is to blame? usually just run the recommended quick scan settings. recently upgraded to ASC 6 Beta 1.1, that might have been the last program I was able to successfully install.

running Windows 7 (64-bit) Home Premium Ed
on a fairly new HP Pavilion Elite (HPE-410f).

if someone is willing to offer some guidance as to how I can resolve this problem, I'd be willing to offer $ compensation. not under warranty w/ HP & don't want to pay someone in Pakistan $100 for 30 mins of them reading from a prompt & not getting anything accomplished. let me know if you can help, and if you need any additional details on my part. thank you so much!