How are you "uploading" or "downloading" or using "Save as" while in Safe Mode on the internet? Even in "Safe Mode with Networking", it's not a good method.. If you're seeing and error message when the computer crashes, EXACTLY what is the message?

A three year old laptop is nearing its end, but here are a few things to try.

First, have you used regularly used compressed/canned air to blow out all the dust from around the vents and inside the computer cover? If not, please do.. Heat can cause lock ups and crashes, etc.

2. You mentioned that its Windows 7, but have you also installed Service Pack 1 and kept current with Windows Updates? If not, please do.

3. If you've got both Avast and Norton installed on the computer, that's not a good thing and could be causing part of the issue.. You should only have one AV running at a time.. Uninstall one or the other and leave it that way. Such programs frequently conflict when scanning uploaded/downloaded files and it could be causing the problem.

4. Unfortunately, both of the programs you have installed fail on a number of types of malware.. Have you tried the standalone Malwarebytes program yet.. If not, please do, from the link below, as it won't conflict with the other AV because it doesn't run in real time.

http://www.filehippo.com/download_malwarebytes_anti_malware/

Hope this helps.

Grif