Someone hijacked my email address

I tried to download HijackThis as instructed but it said it was denied. There was instructions but I ran into
problems, I am going to post my problem and if someone who is patient can help me get what you need to
resolve this issue I would greatly appreciate it. I am not a computer literate person.

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: Pentium(R) Dual-Core CPU E6600 @ 3.06GHz, Intel64 Family 6 Model 23 Stepping 10
Processor Count: 2
RAM: 3037 Mb
Graphics Card: Intel(R) G41 Express Chipset, 1294 Mb
Hard Drives: C: Total - 935767 MB, Free - 883527 MB;
Motherboard: eMachines, EL1852G
Antivirus: AVG AntiVirus Free Edition 2014, Updated and Enabled

Problem: Yesterday I started receiving multiple Daemon messages being sent to people I don't even
know and people I haven't sent emails to in a long time both businesses and individuals. I am sure it
is some type of virus and don't know what to do. About a month ago ATT sent me an email stating they
thought someone hacked into my email. I called them and they changed some things and I thought it
was okay.

Please help.....