jacobweaver800 :
After doing a bit of searching, you can run Win7 32 bit, you'll need aleast 2gbs of ram for 64 bit
Be aware extended support for Windows 7 is set to expire in Jan 2020. That's when Microsoft is planning to stop releasing security updates for it. Note that Windows 10 also lists 1 GB as the minimum for the 32-bit version. So you may want to opt for Win10 instead. Because CPUs pretty much stopped getting faster (they used to double in speed every ~3 years), software developers were forced to optimize to cut down on software bloat. And as a result by many metrics Win 10 actually requires fewer resources than Win 7.
https://support.microsoft.com/en-us/help/13853/windows-lifecycle-fact-sheet
If you don't want to pay for a Windows license, I would suggest either Ubuntu or Linux Mint. Both currently list 1 GB as a minimum, 2 GB recommended.
Ubuntu is by far the most popular Linux distro, but it uses a UI which a lot of people have complained about. The regular versions are released every 6 months, with 9 months of support - you're expected to upgrade to the newest version for continued support. Every 2 years they release a LTS (long term support) version which will get updates for 5 years before they expect you to upgrade to a newer version. The next LTS release is set for April 2018.
https://www.ubuntu.com/desktop
Mint is basically Ubuntu with the UI replaced with something more similar to Windows. So it may be easier to use if your aunt already comfortable with Windows. Their releases are based on the Ubuntu LTS releases. So the current versions are supported until April 2021. The next release (after the April 2018 Ubuntu LTS release) will be supported until April 2023.
https://linuxmint.com/download_all.php
Xubuntu is probably good too, I just haven't tried it out yet.
While that CPU is capable of running 64-bit software, I'd suggest sticking with the 32-bit versions. The 64-bit versions require slightly more RAM because it increases the smallest memory size for variables from 4 bytes to 8 bytes. Consequently the exact same software recompiled for 64-bit requires more RAM than the 32-bit version.
An easier way to install Skype for Linux was just released.
https://www.omgubuntu.co.uk/2018/02/install-skype-linux-ubuntu