Latest drivers for this device can be found at the Oki.com a small cache of publicly available below.
OKI ESC/P Printer Driver
File: okiML300T700 WinXP_tcm3-174093_42812.zip
9c73f66ba756a08260924c21dbc7427dd115c0d5d20363ca15e9a8c07aefce93
OKI Microline 321 Turbo Plus User Manual
File: ML320T_PH_63082.pdf
ee0e93e8d1844fe16de17f70fee138973a97613abbedd185e444b34bf3557683
Printer Output Type: Monochrome
Printing Technology: Dot Matrix
Connections: Wired USB
Duplex: No
1. Extract the downloaded zip file.
2. Launch Add Printer Wizard.
3. When prompted for the Manufacturer and Model click on Have Disk.
4. Browse to the extracted location.
5. Click OK.
6. Follow the prompts to finish the driver installation.