The recent soar in certain company stocks are offering finance executives with a brief window of opportunity to tap fresh sources of funding. However, not all of them are likely to cash in, as it takes time to prepare an equity sale, and business risk increasing the ire of regulators if the share price crashes after a fundraising round.Corporate advisors say more companies have asked about how to prepare for a possible equity sale or another fundraising event in recent weeks as stock prices went up.A few have already taken the opportunity. Power Plug Inc., a hydrogen fuel-cell company that witnessed a roughly eightfold increase in its stock price over the past six months, on Tuesday said it was planning to increase roughly %1.8 billion by selling stock, roughly $300 million more than initially planned. AMC Entertainment Holdings Inc. this week increased more than $300 million in equity sale. On Wednesday, its share price more than tripled.Individual investors are piling into companies that many once saw as a weak bet. Shares of GameStop Corp., the video game company, increased more than 130% Wednesday. Other stocks, including those of BlackBerry Ltd., Bed Bath & Beyond Inc. and Eastman Kodak Co. aksi saw big gains on Wednesday.