The steps required to adjust Metastock data for symbol or company name changes is called merging. The steps to merge Metastock data are shown below
We are required to merge the data of two equities when the symbol of the company changes (this could even happen due to a name change). In that case you will notice that no data will be downloaded for the old symbol after the change date. Instead data will be downloaded for the new symbol since the change came into place
After the symbol change the data will be downloaded for the new symbol. In that case if you open the chart you will have incomplete data for your analysis. All figures are still existing in the old data, so this data needs to be brought in the new symbol data, so that we can get the complete historical information. This step is called merging. For example see the image below.

In the above figure we see that there is no data downloaded for MPHASISBFL (old symbol) after 22-Dec-2006 and the data download for MPHASIS (new symbol) started on 26-Dec-2006.So in case you are doing your analysis on 30-Dec-2006 using the data of MPHASIS (new symbol) you hardly have any information to base your analysis, additionally you cannot use the data in MPHASISBFL (old symbol) as it does not have the most critical data of the last few days.
Hence you need to get the data of MPHASISBFL merged into MPHASIS.
Start 'The Downloader' utility available with Metastock.
Goto Tools >> Merge
The following window opens. In that select the old symbol in the left list (Source) and the new symbol (destination) in the right list. The data will be copied from source to destination i.e. from MPHASISBFL to MPHASIS.

Click on the options button and set the options as shown below

Click OK to close the options window.
Click Merge to merge the data.
The data will get merged and the source (i.e. old symbol) will be deleted.
So now if you check the chart of MPHASIS (i.e. new symbol) it will have complete data.