I downloaded bit defender andit doesnt show up in windows search but it does show up under extensions in addon manager
- BitDefender QuickScan Web Netscape Plugin
- Adobe PDF Plug-In For Firefox and Netscape 10.1.0
- Windows Presentation Foundation (WPF) plug-in for Mozilla browsers
- Next Generation Java Plug-in 1.6.0_26 for Mozilla browsers
- NPRuntime Script Plug-in Library for Java(TM) Deploy
- Shockwave Flash 10.3 r181
- Npdsplay dll
- DRM Store Netscape Plugin
- DRM Netscape Network Object
- User Agent: Mozilla/5.0 (Windows NT 4.0; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
How did you download it?
Does it appear in Firefox's download manager (Ctrl+j)? In that case you should be able to find it by right-clicking it and choosing Open Containing Folder.
Your browser is identifying your OS as Windows NT 4, which is very rare these days. If it is incorrect (e.g., you run Windows 2000, XP, Vista or 7), then this article might help: Websites or add-ons incorrectly report incompatible browser | Troubleshooting | Firefox Help.