Can I use windows xp to convert quickbooks online to quickbooks desktop 2018?

You may try it on any Windows OS (e.g XP, Win 7). You should try these step as well

https://quickbooks.intuit.com/learn-support/en-us/install/can-i-export-qb-online-to-desktop-i-found-...

Some things to check

Have you received the newest updates on QB2018? 

Have you tried downloading the free trial of QB2020 and then trying that?  Be aware that if it works, your downloaded and the converted file will be only for QB2020 and is not backward compatible (and you cannot license the free trial or even attempt to as it will freeze up solid)

If this is only for archival purposes and possibly only your CPA (or the IRS) would need access then an archived 2020 edition company file should serve the purpose.

Thank you for the detailed instructions. Took a few days to get the old computer updated and I am still having issues. 

I go to login to quickbooks online and cannot get to the sign on/log in screen. Am getting the following errors:

Syntax error

login     Line:444

Expected identifier

dojo.js  Line: 82

'console' is undefined

hello     Line: 166

Code: 0    Char: 13

URI: https://c9.qbo.intuit.com/app/hello?localguest=true

Any thoughts on how to bypass this?

Hi Lgpmaui,

If you haven't done the browser troubleshooting steps, you can perform them. Then, try exporting your data again. If the same thing happens, please contact our Support to check this further using their screen-sharing tool.

1. Log in to QuickBooks Online using a different browser.
2. Click on Help and choose Contact Us.
3. Paste your question in the text box and click Let's talk.
4. Choose between Message an agent or Get a callback. These options are available during their office hours.

You can ask the QBO support for your options to let you close your books.

If you have additional concerns, please don't hesitate to post go back to this thread.