When you move or copy a worksheet from one workbook to another workbook in Microsoft Excel 2010, unused styles are unexpectedly copied to the new workbook. In this situation, the file size of the target workbook is larger than expected.
To resolve this issue, apply the following update:
2598143 Description of the Excel 2010 hotfix package (Excel-x-none.msp, Graph-x-none.msp): April 24, 2012
Registry key information
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in WindowsAfter you install the hotfix package, to have us enable the hotfix for you, go to the "Here's an easy fix" section. If you prefer to fix this problem manually, go to the "Let me fix it myself" section.
Here's an easy fix
To enable the hotfix, click the Download button. In the File Download dialog box, click Run or Open, and then follow the steps in the easy fix wizard.
Install hotfix that is described in Microsoft Knowledge Base (KB) article 2598143 before you run the easy fix solutions.
This wizard may be in English only. However, the automatic fix also works for other language versions of Windows.
If you’re not on the computer that has the problem, save the easy fix solution to a flash drive or a CD, and then run it on the computer that has the problem.
For Windows 8
For Windows 7, Windows Vista, Windows XP, Windows Server 2008 or Windows Server 2003
After you install the hotfix package, follow these steps to enable the hotfix:
Click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then select the following registry subkey:
On the Edit menu, point to New, and then click DWORD (32-bit) value.
Type DisableCopyUnusedCustomStyles, and then press ENTER.
In the Details pane, right-click DisableCopyUnusedCustomStyles, and then click Modify.
In the Value data box, type 1, and then click OK.
Exit Registry Editor.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.