Can't open this app: Claude Desktop won't start on Windows — fix it with Repair without losing your sessions
You try to open Claude Desktop on Windows and instead you get a dialog headed "Can't open this app", telling you that "You'll need to go to advanced options for Claude and select Repair" — and doing exactly what it says works. No uninstall, and no Reset that throws your data away. There is, however, one step in the middle where people actually get stuck, and it is the centre of this article. Clicking Repair can come back with a message telling you the app is still running, even though no Claude window is open anywhere. The cause is that Claude Desktop keeps running in the system tray after you close its window, and while that resident process is holding the package files open the repair cannot go through. The fix is simple: end the processes explicitly, then click Repair. And that fact points at the cause of the failure itself — the same process broke the update and then blocked the repair. The article also answers the question most people ask first: do your sessions get wiped? The answer splits three ways. Your claude.ai conversation history sits on Anthropic's servers and is untouched. Claude Code sessions live under %USERPROFILE%\.claude\projects\, outside the app package, so they survive a repair, a reset and even an uninstall (a real machine held 2,977 files, roughly 3.0GB, across 52 projects). The only thing at risk is the app-side settings in %APPDATA%\Claude, and Repair keeps even those — Windows spells the difference out on the screen itself, with Repair saying the app's data will not be affected and Reset saying the app's data will be deleted. From there it covers the read-only PowerShell state check, a backup routine, a staged escalation when the app still will not open (checking that vmcompute and hns are running, reinstalling with -PreserveApplicationData), the inferred cause of a half-registered MSIX alongside the GitHub issues (#55465, where the install succeeded but no entry point was created, plus #50285 and #48437 — all closed as not planned with no official fix), how to lower the odds of a repeat, and a comparison with the old installer build, where the latest MSIX release and an old-format machine both measured 1.24012.9.