When buying a computer or laptop, how do you know it is safe from spam, do you install/buy disks? Anything for advice can be helpful?

Mcafee as a decent  variety of pc cleaners,they gobble up spam too,realtime protection,,use googleys adblocker,they are ineffective when media sites like fakebook embed  factchecking propaganda

Ummmm....the only way to be safe from spam is to NOT buy a computer or laptop

i build a new computer and have have zero issues with anything on the HDD/SDD -- of course, in part, that's becuase formatting the drive [required] wipes out all pointers to anything that was on it when i got it

This is what I do:

1. Desktop Computer:  I build it my self with a Clean Install of Windows.

2. Laptop Computer:   Reformat the Hard Drive and do a Clean Install of Windows. If the Laptop has the older SATA Mechanical Hard Drive I would replace it with a SSD.

The Store where I recently purchased a HP Probook did exactly that.  Performed a Clean Install of Windows.  This Wipes out all programs on the Hard Drive.

spam is what you receive in emails

do you mean malware or viruses

if so

run an antivirus program

or format the machine and install a fresh copy of the operating system

If your computer or laptop has not already been factory reset then you do a factory reset and it reinstalls a brand new version of Windows all by itself in about an hour