I’ve used multiple machines over the years for my main server which also handles weather stuff. I’m quite fond of my current machine.
The total disk space used is 4.61GB for my current weather partition. This includes WD itself, my site files, WD backups, downloads (WD updates and the like) as well as my archives for my old CW numbers that go back to April 2009. All my stuff (C: system OS, D: network services, & E: weather) fit on a 36GB SCSI disk for a number of years, but I didn’t have or work with any videos. As far as SSD, WD and all these programs make lot of writes which SSDs having a write lifetime you’ll have to keep track of the wear leveling and migrate to another disk as its life nears its end which could be several years out.
Yes, you can run apache on windows. I did it for 4 years and hosted 3 different domains using the server from my house (not recommended). If you must run IIS and this machine is accessible from anywhere on the internet, you best make sure you keep it patched. IIS is a popular service to get probed and/or hacked.