Perhaps for third party software but an operating system like Windows 2000 is obsolete because there is a newer, better version for sale and Microsoft clearly does not offert support for it.
‘Microsoft no longer uses SHA-1 to authenticate Windows operating system updates due to security concerns associated with the algorithm, and has provided the appropriate updates to move customers to SHA-2 as previously announced. Accordingly, beginning in August 2019, devices without SHA-2 support have not received Windows updates.‘