check the NTFS permission settings of that documents folderbut if you're an administrator, you should be able to do that anyway....
Do one of the following solutions:
Solution 1: Temporarily disable simple file sharing and change permissions. (Windows 2000 and XP Pro).
Disable simple file sharing (Windows XP Pro only) and change the permissions for the All Users folder. Then install Acrobat. After installing Acrobat, reenable simple file sharing.
To temporarily disable simple file sharing and change permissions:
1. Log in as an administrator.
2. If you use Windows XP Pro, disable simple file sharing (if you use Windows 2000, this step is not necessary):
a. Choose Start > My Computer.
b. Choose Tools > Folder Options, and then click the View tab.
c. In the Advanced Settings section, deselect Use Simple File Sharing (Recommended), and click OK.
3. In Windows Explorer, open the Documents and Settings folder.
4. Right-click the All Users folder, and then choose Properties.
5. Click the Security tab.
6. Click Administrators in the User list. If Full Control is not selected in the Permissions list, change the access control level to Full Control . (For more information on how to modify access control levels, see the Microsoft documentation.)
7. Click Advanced, and select Replace Permission Entries On All Child Objects With Entries Shown Here That Apply To Child Objects (Windows XP Pro ) or Reset Permissions On All Child Objects And Enable Propagation Of Inheritable Permissions (Windows 2000).
8. Click OK, and then click Yes. Click OK to close the All Users Properties dialog box.
9. Install Acrobat.
10. If you use Windows XP Pro, reenable simple file sharing (if you use Windows 2000, this step is not necessary):
a. Choose Start > My Computer.
b. Choose Tools > Folder Options, and then click the View tab.
c. In the Advanced Settings section, select Use Simple File Sharing (Recommended), and click OK.
Solution 2: Change the sharing permissions, and then install Acrobat. (Windows XP Home Edition).
1. Choose Start > Run, type %allusersprofile% in the Open box, and then click OK.
2. Right-click the Shared Documents folder, and choose Properties.
3. Click the Sharing tab, and select Share This Folder.
4. Click Permissions, and select Everyone from the Group Or User Names section.
5. Select Allow next to Full Control in the Permissions section, and click OK. (For more information on changing permissions, see Windows Help.)
6. Click OK to close the Shared Documents Properties dialog box.
7. Install Acrobat.
Solution 3: Change permissions in Safe mode, and then install Acrobat. (Windows XP only).
1. Choose Start > Run, type msconfig in the Open box, and click OK.
2. Click the BOOT.INI tab, and then select /SAFEBOOT in the Boot Options section.
3. Select MINIMAL from the /SAFEBOOT options, and click OK.
4. Restart Windows.
5. Choose Start > Run, type %allusersprofile% in the Open box, and click OK.
6. Right-click the Shared Documents folder, and choose Properties.
7. Click the Security tab.
8. Select Everyone from the Group Or User Names section, and select Allow next to Full Control in the Permissions section. (For more information on changing permissions, see Windows Help.)
9. Click Advanced, and select Replace Permission Entries On All Child Objects With Entries Shown Here That Apply To Child Objects.
10. Click OK, and then click Yes.
11. Click OK to close the Shared Documents Properties dialog box.
12. Choose Start > Run, type msconfig in the Open box, and then click OK.
13. Click the General tab, and then select Normal Startup - Load All Device Drivers And Services.
14. Click OK, and then restart Windows.
15. Install Acrobat.