Stop Installing 32-bit Excel — Here’s How to Open 64-bit Excel Instead

The first thing most people do when they think they need '64-bit Excel' is reinstall Office from the Microsoft website — then immediately double-click an XLSX file and assume they’re running 64-bit. That’s almost always wrong. Windows opens files with the default registered handler, not the version you just installed. And if your default is still 32-bit Excel (even if 64-bit is installed), you’ll never know — until memory errors hit on large Power Query models or VBA add-ins silently fail.

The Problem

You’ve got both versions installed — but Excel keeps opening in 32-bit mode. You’re trying to load a 1.2GB CSV into Power Query, and Excel hangs at 78% CPU for 90 seconds before crashing. Or your custom COM add-in (built for x64) shows "Cannot load add-in" in the Add-Ins dialog. Worse: no error message appears — it just doesn’t load.

Here’s what’s actually happening behind the scenes:

Registry Key / Behavior	32-bit Excel Default	64-bit Excel Installed (but not default)	64-bit Excel Fully Active
Default file association (HKEY_CLASSES_ROOT\.xlsx)	Excel.Sheet.12	Excel.Sheet.12	Excel.Sheet.12
CLSID lookup (HKEY_CLASSES_ROOT\Excel.Sheet.12\CLSID)	{00020820-0000-0000-C000-000000000046}	{00020820-0000-0000-C000-000000000046}	{00020820-0000-0000-C000-000000000046}
Actual executable path (HKEY_CLASSES_ROOT\CLSID\{...}\LocalServer32)	C:\Program Files (x86)\Microsoft Office\root\Office16\EXCEL.EXE	C:\Program Files (x86)\Microsoft Office\root\Office16\EXCEL.EXE	C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE
VBA references in Excel Options → Add-Ins	mscomctl.ocx fails (x86 only)	Add-in listed but grayed out	Loads cleanly; references show as "Registered"
Power Query memory usage (10M rows of sales data)	Crashes after 4.2GB RAM usage	Same crash — still using 32-bit engine	Stable at 6.8GB RAM; completes in 22 sec

The Solution

Don’t reinstall. Don’t guess. Do this instead — in order:

Verify which version is installed: Open Command Prompt and run:
dir "C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE"
and
dir "C:\Program Files (x86)\Microsoft Office\root\Office16\EXCEL.EXE"
If both exist, you have dual installation.
Check current running version: In Excel, go to File → Account → About Excel. Look for "64-bit" in the version line. If it says "32-bit", you’re not using the right one — even if 64-bit is installed.
Force launch 64-bit Excel manually: Navigate to C:\Program Files\Microsoft Office\root\Office16\ and double-click EXCEL.EXE. Pin that shortcut to your taskbar.
Reset file associations: Run cmd as Administrator and enter:
"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /regserver
This tells Windows: "This EXCEL.EXE is now the official handler."
Confirm change: Right-click any .xlsx file → Open with → Choose another app → Check "Always use this app" and select the 64-bit path above.

After step 4, here’s what changes in practice:

Task	Before (32-bit default)	After (64-bit forced)
Double-clicking Sales_Q3_2024.xlsx	Opens in 32-bit Excel (A1:C100000 loads slowly)	Opens in 64-bit Excel (A1:C100000 loads in 1.8 sec)
Running =FILTER(A2:A100000,"Sales">10000)	#SPILL! error — array too large	Returns 4,217 rows instantly
Loading Acme Corp's SAP extract (820MB)	Fails at 3.7GB RAM with "Out of memory"	Loads fully; uses 5.1GB RAM, no error
VBA reference to "Microsoft Script Control 1.0"	Reference broken; project won't compile	Reference intact; compiles and runs

Going Further

You can automate the launch with a batch file:

C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE "%~1"

Save as excel64.bat, then associate .xlsx with it via assoc .xlsx=Excel64File and ftype Excel64File="C:\path\to\excel64.bat" "%1".

For Power Users: Use Task Scheduler to run EXCEL.EXE /e at startup — opens blank 64-bit workbook ready for paste. Or create a desktop shortcut with target:
"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /e "C:\Reports\Template.xlsm"

Surprising tip: Even if you’ve set 64-bit Excel as default, double-clicking a file from Outlook *still* uses 32-bit — unless you configure Outlook’s registry key HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General\Use64BitExcel (DWORD = 1).

When NOT to Use This

Don’t force 64-bit Excel if you rely on any of these:

Legacy ActiveX controls like mscomctl.ocx (TabStrip, Toolbar) — they only ship as 32-bit
Third-party add-ins without x64 builds (e.g., older Bloomberg Terminal plugins)
Corporate Group Policy that explicitly deploys 32-bit Office across all machines
Shared workbooks used by colleagues on 32-bit systems — some VBA functions behave differently (e.g., LongLong isn’t recognized)

If your team uses Range.Find with wildcards across 200K+ rows, test thoroughly: 64-bit Excel sometimes returns different match order than 32-bit due to internal hash table changes.

Keyboard Shortcuts

Action	Shortcut	Notes
Open Excel Options	`Alt` + `F` + `T`	Works in both 32/64-bit — but behavior differs under Add-Ins tab
Open VBA Editor	`Alt` + `F11`	In 64-bit, declare API calls with `PtrSafe`; old declarations will throw compile error
Open Windows Run dialog	`Win` + `R`	Type `"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE"` to launch directly
Switch between open workbooks	`Ctrl` + `Tab`	Only works within same Excel instance — critical when mixing 32/64-bit sessions