something is screwing up my computer.

i have to re-enter my passwords, even if i've just visited a site, and even if i checked 'keep me logged in'. i have to do it all over again the next time i go there. also, the icons from my toolbar at top of browser appear and disappear. also, system restore seems to run, then after reboot it says it didn't work. also, i hear ads audio and can't figure out the source of them. many, many more nuisances. i have run spybot and avast free, but still have the problems. thanks for helping me,

Boyd.

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) i3-2350M CPU @ 2.30GHz, Intel64 Family 6 Model 42 Stepping 7
Processor Count: 4
RAM: 4043 Mb
Graphics Card: Intel(R) HD Graphics Family, 1797 Mb
Hard Drives: C: Total - 584792 MB, Free - 373803 MB; D: Total - 21422 MB, Free - 2278 MB; E: Total - 4055 MB, Free - 10 MB;
Motherboard: Hewlett-Packard, 1695
Antivirus: avast! Antivirus, Updated and Enabled