A once highly regarded Silicon Valley computer whiz has filed court documents alleging that he was forced to plead guilty to a scheme of stealing computer secrets to sell to the Soviet Union. Kevin Eric Anderson has filed a series of affidavits in federal court in San Jose, saying that his attorneys told him that he could never win acquittal and that exaggerated national security claims by prosecutors led prison officials in Texas to wrongly classify him as a convicted spy. Anderson pleaded guilty last May to conspiring to violate export laws and to wire fraud. He was sentenced to six years in prison. Prosecutors contended that the secrets he stole were proprietary information for Saxpy Computer Corp. of Sunnyvale and that the Saxpy computer was a supercomputer with military application that could help the Soviets build a “star wars” system. They later toned down the claim, saying it was a “near-supercomputer.” Nothing was exchanged with the Soviets, although wiretapped conversations indicated that Anderson thought he could sell the material to them for millions of dollars.