Articles are added before countable nouns, when reffering to softwares Windows, MS Office, Adobe, etc you are referring to make or company which cannot be counted.
Instead you can always say..
Insert the Windows CD in the drive. (CD is countable)
While talking about Dell or Acer, you are reffering to the laptop or computer not the company.
I have a DELL laptop. (laptop can be counted)
However if you use Dell without the laptop, you wont use article, ex.
Dell is the biggest manufacturer of laptops in US.
I like Acer laptops. (over her though word laptop is use but it is used to refer to the company not the phsyical laptop)
Hope you the point.