I absolutely understand
@amorosik's desire for that older version. If it is going to run on an older computer, then compatibility won't be an issue. However, there are considerations as time goes on. Even if you intend to leave things in their older state, time IS marching on around you. Two scenarios come to mind.
One is that if this is an old version of Access on a newer computer, automated Microsoft patching has become insistent these days. You can hold off patching for a while, but Win10 only lets you block patching temporarily. At some point it will say (in effect) "I'm going to patch you now. Shutting down...." and you can't stop it unless you are a registry hack wizard. At which point (and based on past behavior including posts in this forum) some patch will kill some element of the older Office library and you are done.
A second scenario is that you are running this archaic software and you have to expose it to the Internet in some way. So you have an anti-virus package. Because you are maintaining backwards compatibility for Access, you have to continue to run an older version of Windows. Just because the hackers are modernizing, they are still looking for "low-hanging fruit" to pluck. And older versions of Windows have SO many known vulnerabilities. Eventually your A/V package that handles that clunking old version of Windows is no longer updating because the A/V vendor ALSO has to have a limit on how much support to offer based on dollar value offered by supporting that older O/S. It comes back down to "Does support of DOS 6.2/Win 3.1 by our package return enough to cover the cost of that support?"
Some years ago, long before my Navy job, I worked for a company that made industrial control systems that included building energy management for multi-acre factories with HVAC control encompassing dozens of "zones" to be kept warm or cold on particular schedules. We had a customer in the Michigan area who was getting a system just as my employer got bought out by typical corporate issues, mostly cash flow and an incredibly optimistic AND STUPID vice-president of Marketing.
The new company president was asked about a support issue and I overheard him ask "How much more money do they owe us on our current contract?" When he got the answer, about $12K, his response was "Screw them, write off their last payment and let them purchase support at our new rates." (This was maybe 40 years ago.) He was ignoring the warranty because a loophole in his state laws allowed him to drop warranties that were part of a buyout. Now I'm seeing the same issue in Microsoft, a hard-nosed and callous disregard for customers when the dollar value is not there and they don't see it as impairing their public image.
The CrowdStrike issue WILL get fixed because public image is going to radically affect future sales. Trust me, the dollar value of "image" has been well and thoroughly calculated. But as to support for Access 2003, which is 21-year-old software, the public image dollar value is nil. If CrowdStrike doesn't support their "Falcon" package, they might as well close their doors. But if Microsoft stops supporting Access 2003... wait a minute, they HAVE done so... and they are still open.
By the way, regarding 2003's User Level Security, that was the MDAC module... Microsoft Data Access Control. In about 2005, the SANS Corporation's "top 20 riskiest software" list had MDAC as #5. It was insanely easy to spoof. Let's be honest, Access is not the hardest package in the world to hack.