Internal error 6401

I'll be really interested in seeing if someone (maybe John Pollard?) can help you on a release of Quicken that is 29 years old on an operating system that hasn't been around for decades as well! Good luck my friend!

Given that the earliest version of Quicken I ever used was Q2000 for Windows, and that the most current Quicken version I have installed is Q2002 for Windows (which I rarely have occasion to look at); I can only offer a minimally useful guess as to the meaning of the error message.

I suspect that "Internal error 6401" is coming from the internal data base software that your Quicken version uses (*), and its literal meaning will be totally unhelpful for addressing your problem (it might have helped Intuit support, had you experienced the problem and reported it to Intuit back when your Quicken version was covered by support).

And since the versions of Quicken that I have do not employ any of the terminology you have supplied, I'm not really certain what you're doing or where you are in Quicken.

It sounds like you might be trying to delete ("trim") some Quicken historical prices. Based on that assumption ...

In Q2002 I can delete one, or more, historical security prices by going to: Investing > Portfolio view, right-clicking a security and selecting Price History". That presents me with a window listing all prices for that security (14 prices at a time) with Date, Price, High, Low and Volume as columns - and New, Edit, Delete, Print, and Close in the Price History menu row.

If I select one Date/Price row in the Quicken Price History window and click Delete, the price for that date will be deleted.

I can also select multiple Date/Price rows (selecting rows as I would select multiple files in Windows Explorer - possibly not available in DOS versions of Quicken), then click Delete - Quicken will then delete all the selected Data/Price rows.

If you are unable to delete a single Quicken security price, at a place where Quicken intends to allow you to delete a security price, you may have some data corruption. If I thought I had that problem in Q2002 for Windows, I would try (with a healthy dose of skepticism) to "Validate" my Quicken data. I can do that by going to File > File Operations > Validate. That process will NOT find, nor fix, all problems.

If you are, in fact, trying to delete historical prices, another option might be to "correct" those prices instead of deleting them. In Q2002 I can do that in the aforementioned Price History dialog, or in Investing > Portfolio View by selecting the desired "As of" date and manually keying the correct share price in the field at the intersection of the row for the security in question and the column labelled "Price".

Based on what you have posted so far, that's the best I can offer.