It's not possible to know without the earlier detections, esp the one that prompted you to run the boot scan.
In your screenshots the detection relates to an item in a restore point. Possibly Avast is unable to process it because the restore point is too large for the chest, or is locked. This can be easily removed by cleaning all restore points. (instructions below.)
First, I would get a second opinion from a good demand scanner, such as
MBAM. Install the free version, update it, run a quick scan, and post the scan report.
Prior to doing this you may want to run a disk cleanup, using the built in disk cleaning utility in Windows. (Start>all programs>accessories>system tools>disk cleanup).
To delete restore points (and any contained malware within) go to "control panel>system", or right click the "my computer" icon and select "properties", select the system restore tab, then tick "turn off system restore on all drives". Reboot. Turn it back on again.
You are using an out of date version of Windows, SP3 has been available for some time and addresses several vulnerabilities.
I recommend updating to the latest version of Avast at some point. Likely that this year sometime version 4.8 will no longer be supported.