Wrong icon in task bar

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: AMD E-450 APU with Radeon(tm) HD Graphics, AMD64 Family 20 Model 2 Stepping 0
Processor Count: 2
RAM: 3686 Mb
Graphics Card: AMD Radeon HD 6320 Graphics, 384 Mb
Hard Drives: C: Total - 465640 MB, Free - 258912 MB; D: Total - 11196 MB, Free - 1022 MB; H: Total - 953867 MB, Free - 221875 MB; I: Total - 953835 MB, Free - 72599 MB; L: Total - 152617 MB, Free - 135895 MB; O: Total - 953866 MB, Free - 154740 MB;
Motherboard: PEGATRON CORPORATION, 2AD1
Antivirus: avast! Antivirus, Updated and Enabled


I have a weird problem. every time I open a PDF file on the task bar instead the Adobe PDF reader icon i get the icon for a different pgm(always the same one). I checked the pgm it shows the correct icons so how can I fix it?