Discontinuing Windows NT versions of its Alpha processor-based servers and workstations will cost Compaq Computer Corp up to $250m over the next two quarters, the company’s latest filing with the US Securities and Exchange Commission reveal. Compaq will book a one-time charge of $50m to $100m against its earnings for the fourth quarter to December 31 plus a one-time charge of $100m to $150m in its first-quarter 2000 earnings, according to it’s 10-Q report covering the third quarter to September 30.

Under a previously-announced plan, customers who have purchased the NT/Alpha systems will be offered 90% credit toward a new Intel/NT workstation or server. Customers opting to remain on Alpha will be offered a free upgrade to an Open VMS, Tru64 Unix or Linux system.

Compaq had not flagged the charges in its initial third-quarter earnings report announced on October 26. However under SEC rules it had up to 45 days after the close of the quarter to deliver a full 10-Q report disclosing expected future liabilities.