This excerpt taken from the NVDA 10-K filed Nov 29, 2006.
Property and Equipment
Property and equipment are stated at cost. Depreciation is computed using the straight-line method based on estimated useful lives, generally three to five years. Depreciation expense includes the amortization of assets recorded under capital leases. Leasehold improvements and assets recorded under capital leases are amortized over the shorter of the lease term or the estimated useful life of the asset.