MT4 Overwriting Historical Data

I'm hoping one of you guys who are more familiar with the platform than I can help me out with this problem. I've been trying to import M1 data from FXDD. The import works fine, and I can see the M1 data on the chart. For a little while. Apparently when the chart is updated, all of the imported data is removed from view, although the number of records in the history center still seems to reflect that the data is still there somewhere. Is there any way for me to preserve the historical data I've imported during a live market?

I've also had some difficulty using the period converter script (the opt. one wouldn't load for some reason) to get the higher time frames to generate from the M1 data. I'm sure I'm doing something stupid!

Thanks in advance.

you could navigate (with eg. windows explorer) to the history-folder, right click the files and set in the properties to "read only".
This should prevent mt4 from overwriting exisiting files ...

Thanks, I got it to work. Not sure why the data was disappearing on me but it's stopped doing so now. As for the period converter, if anybody else comes searching, here's a link to a good set of instructions for how to use it correctly. I assumed that it would write the bars to the chart automatically but you have to import them.