This is what endnote says about accessing styles
“Accessing Styles in Other Places
The Style Manager displays only the styles in the chosen styles folder. Only styles from one folder can be displayed in the Styles menu at any given time; styles in subfolders within the selected folder are ignored.
By default, the Style Manager displays the styles that are in the “Styles” folder in the EndNote folder. You may copy files into this folder to have them displayed in the Style Manager, or you may change this to use a different folder, if necessary. To do so, choose Preferences from the Edit menu, select the Folder Locations panel, and click the Select Folder button in the Styles section of that panel. ”
One approach is to copy C:\Program Files\EndNote X\Styles to the U: drive and then change the EndNote preferences to point to U:\Styles.
Call or e-mail the Help Desk if you need assistance.