Network Associates Inc., the No. 1 security software maker, said it has completed its $705.7-million purchase of Dr. Solomon's Group, adding Britain's top computer anti-virus maker. The company exchanged 0.82875 share for each American depositary receipt of Dr. Solomon's. Network Associates has been on an acquisition spree since it was formed in December through the merger of McAfee Associates and Network General. Santa Clara-based Network Associates is battling Symantec Corp. in the market for software that guards against computer viruses, and Dr. Solomon's gives it important products and an extensive list of overseas customers. The company will take a third-quarter charge of 1 to 2 cents a share for the purchase. Network shares rose $3.13 to close at $49.25 on Nasdaq.