Can't install Dap extension for Chrome

you can just do a clean installation of chrome and start over if its malfunctioning. you can delete the folder in this location C:\Users\[your user name]\AppData\Local\Google\Chrome\

You seem to have been trying to install an older version of DAP. Get the current one from here:
http://www.speedbit.com/dap/download/

The DAP Extension for Google Chrome allows you to use DAP to accelerate your file downloads while using the Chrome browser.Download Accelerator Plus (DAP) automatically activates when you download files from Internet sites using your web browser. DAP is configured to be activated by the most common file types (EXE, ZIP, MP3, ARJ, RAR, LZH, Z, GZ, GZIP, TAR, BIN, MP3, AVI, MPG).

To manage the extensions that will activate DAP, open DAP's main window and click the Tools menu, and then click Options. The Options window appears. Click Advanced, and then click Ignore File Extensions (works only with FireFox browser). The Ignore File Extensions window appears and you can add any file extension that you do not wish to download with DAP.

You can also download files with extensions that do not appear in DAP's configuration. Simply right-click a download link on a webpage, then in the shortcut menu that appears click Download with DAP. This option is available with Internet Explorer, Firefox and Google Chrome.