(FORTUNE Magazine) – For a solid year, tech-stock investors dreaded the millennium computer glitch, the self-fulfilling prophecy that caused billions of dollars to be diverted from software and hardware purchases so that existing systems could get a proper scrubbing. Old-line mainframe companies like IBM and Unisys were the most obvious victims of this spending diversion, followed by PC and peripheral manufacturers that sell mainly to corporate clients. Now that it's clear the Y2K bug was killed in its larval stage, however, many analysts say that deferred orders are about to pour in and send computer stocks flying.

Careful, though. Y2K was only one factor weighing on these computer makers. In some cases other issues may keep a lid on their stock price, despite the end of the premillennial sales drought. And contrary to expectations, some of the companies that stand to get the biggest boost from Y2K's quiet passing don't make computers.

There's no doubt, however, that the companies hardest hit by Y2K fears were mainframe companies like IBM and Unisys. Their best customers, FORTUNE 500 companies with huge legacy computer systems, had no choice but to divert attention to fixing software. Now comes the rebound. "There's a significant amount of pent-up spending to be done by the FORTUNE 500 on new systems and Internet infrastructure," says John B. Jones Jr., enterprise hardware analyst for Salomon Smith Barney.

Jones thinks that Unisys in particular is set for a rebound because its steep fourth-quarter plunge was so unjustified. A slowdown in its old-line mainframe business dropped Unisys from almost $50 to $21 in October (it has since climbed to about $30), even though "big iron" accounts for less than one-eighth of its roughly $8 billion in sales.

IBM was the most prominent company to blame Y2K for poor earnings, and its rebound immediately after the year's end has been stronger than that of Unisys. However, Big Blue's worries didn't end with the century, warns long-time IBM bull Steven Milunovich of Merrill Lynch. The stock is likely to be hobbled by a slowdown in the growth of IBM's services business, the company's real growth engine, from 15% in last year's second quarter to 8% to 9% currently. "Investors aren't just going to look past [these numbers]," he says, "because the reason they want to own this stock is the services and consulting business."

Dell, the dominant supplier of PCs to big business, should also benefit from a rebound in Fortune 500 spending. True, Dell shareholders didn't suffer as their counterparts at Unisys or IBM did, but in relative terms they had a most un-Dell-like year. The stock was up 39% in '99, way behind the average of 174% for other computer-equipment companies. Catch-up will come, analysts say, but not immediately. That's because Dell now has to face a different Y2K problem: Windows 2000. Microsoft comes out with its long-awaited upgrade in mid-February, and corporations are likely to delay PC purchases until then. That could slow order flow to a trickle in the quarter ending in January. A poor quarter could smack Dell's stock, but so what? It would be a chance to buy the powerhouse stock at a temporary low.

Richard Schutte, who follows PC makers and computer peripheral products for Goldman Sachs, adds the printer maker Lexmark International to the list of potential post-Y2K comebacks. An IBM spinoff, Lexmark tumbled from more than $104 in early October to less than $62 a few weeks later on fears of a sales slowdown. Recently the shares traded at around $90, and Schutte thinks that rise will continue. "Content on the Internet is growing to the point at which everyone is printing everything," he says.

Ironically, some of the tech firms that stand to get the biggest post-millennial bounce are networking stocks, which never suffered from the bug in the first place. Some on Wall Street had expressed concerns that Y2K spending would take away from network business. It didn't. Desperate for gear to make their networks Internet friendly, phone companies spent as though there were no limit to the resources available for technology capital investment, and the stocks cruised through the year's end.

Of course, now that blue chips are no longer distracted by Y2K spending, there really are no limits. Goldman Sachs analyst Ajay Diwan picks Cisco as a top beneficiary of a new wave of Internet spending. Salomon Smith Barney's Jonathan Joseph nominates the white-hot communications chipmaker Broadcom. Says Joseph: "There's no end to how high Broadcom can go."

ADAM LASHINSKY is the Silicon Valley columnist for TheStreet.com. Browse his fortune columns at fortune.com or e-mail him at alashinsky@thestreet.com.