Surging prices for computer hard drives, which are in short supply because of massive flooding in Thailand, are straining the budgets of American consumers. Hard drives, the compact devices that store information in personal computers and other digital machines, have become far more expensive since October - when floods inundated Bangkok and other industrial regions of Thailand, where about 40 percent cq of the world’s supply of hard drives are made, according to market researcher IDC Corp. of Framingham. Fang Zhang, a storage analyst at iSuppli Corp. in Santa Clara, Calif., estimated the drop in hard drive production will be 30 percent cq for the fourth quarter of this year. “Definitely you have a shortage,’’ she said. “You’re going to pay a lot higher than a traditional drive should cost.’’