If you use XP Pro, Home or w2k Pro, try taking ownership of the entire drive. Log on as Administrator or an account with Adm privileges first.
If XP pro, disable Simple File Sharing first (if not already), then right click the drive in question, select Properties, Security tab, click Advanced, select Owner tab. The "current owner" is probably shown as the particular Administrator account on the network.
Underneath it should say, "Change owner to", and then list out the accounts on your computer, which is in the format: [your computer name]\[account name].
(1) Highlight the account name you want to change the owner to. (2) tick the box for "Replace Owner on subcontaines and objects". (3) Click OK.
Then see if you can access the drive. If not, go back to the security tab for your drive, highlight the relevant user account or group, and underneath, change the Permissions. Untick all the Deny boxes, and tick all the Allow boxes (if that's what you want). Click OK.
Procedure for w2k is the same, except there's no simple file sharing to disable. Just go straight to Security tab.
For XP Home, you need to boot into Safe Mode to access the Security tab.