Why do you feel the need to run a boot scan?
Did you run a scan and did avast advise you to run a boot scan?
The only reason to run a boot scan is if avast advises you to do so.
I can't remember the last time avast recommended that I should run a boot scan.
Dell Inspiron, Win7x64 SP1, Pentium Dual-Core T4500, 6 GB Ram, Avast Free v2015.10.2.2214, Comodo Firewall 5.12 w/D+, MalwareBytes Premium 2.0, MCShield, Super Anti-Spyware Free, SpywareBlaster, OpenDNS Premium, Keyscrambler Personal, Ghostery. CCleaner, Greenshot, Firefox (latest build), Google Chrome (latest build) and, various browser security tools.
When you do something, do it with a purpose and do it on purpose.