AVG finds threat but does not heal or remove it.

Hi,
Please find my sysinfo followed by the AVG scan message.


Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows XP Home Edition, Service Pack 3, 32 bit
Processor: Intel(R) Pentium(R) 4 CPU 3.06GHz, x86 Family 15 Model 4 Stepping 9
Processor Count: 1
RAM: 502 Mb
Graphics Card: Intel(R) 82915G/GV/910GL Express Chipset Family, 128 Mb
Hard Drives: C: Total - 53976 MB, Free - 35313 MB; D: Total - 19053 MB, Free - 18978 MB;
Motherboard: Dell Inc., 0JC474
Antivirus: AVG AntiVirus Free Edition 2013, Updated: Yes, On-Demand Scanner: Enabled

AVG scan message:
"";"The file is signed with a broken digital signature, issued by: Microsoft Corporation., C:\Program Files\InstallShield Installation Information\{4F1DA6BF-3614-48A1-9970-9E90F646789E}\data1.cab";"Infected"

Can anyone help me fix this?